Tag: Best Practices

ArcGIS 10 Water Utility Template Updates Webcast

On November 16th at 1:00 PM EST we’ll be giving a
webcast that explores the ArcGIS 10 updates to the Water Utility
Templates.  You can sign up for the
webcast here: http://events.esri.com/info/index.cfm?fuseaction=showSeminar&shownumber=14102

During the hour long webcast, we’ll be focusing on changes
between the 9.3.1 versions of the Templates and the ArcGIS 10 Templates, highlighting
some of the new functionality of ArcGIS 10 that we are leveraging with the
Templates, talking about installation and configuration of the Templates and
demonstrating the Templates in action.

For those who are unfamiliar with the Water Utility Templates,
they are free downloadable configurations of ArcGIS for use in the water,
wastewater and stormwater industries.  So
even if you aren’t using the Water Utilities Templates now, this webcast will
give you an overview of what they are, how they can benefit you and how you can
configure them for your organization.

Posted in Water Utilities | Tagged , , , , , , , , , , , , , , , , , | 2 Comments

Preparing a map for editing: Working on top of imagery

When working with features that are layered over imagery, the default symbology used when creating features and snapping can sometimes blend into the background, making it hard to see what you are editing. In ArcGIS 10, the Editing Options and Snapping Options dialog boxes contain settings for changing the appearance of the edit sketch and snapping symbols. For example, you can set brighter colors for the sketch symbols to make them stand out better and easily trace features on a dark image.

Symbols used when sketching features
When creating lines and polygons, the default edit sketch symbology used to represent the feature’s geometry are green and red squares with a segment line connecting the vertices. You can change the sketch symbols by opening the Editing Options dialog box > General tab. Clicking the buttons opens the Symbol Selector dialog box, where you can choose different colors, sizes, and markers for the sketch symbols. Unselected symbols are the ones you see most of the time when sketching, while the selected symbol specifies how a vertex appears when it is selected after you draw a box around it with the Edit tool or check it in the Edit Sketch Properties window.

When digitizing a hiking trail through a thick forest, change the dark green used to represent vertices to a lighter color. You can also increase the size of the vertex symbols or change the marker symbol altogether. These graphics show the default color and size (left), which is hard to see over this image, and custom settings (right) for the sketch symbols. Play with the symbols to find the right ones for the contents of your imagery and the scale at which you are working.

As you sketch or move a feature, ArcMap by default shows a “what you see is what you get” (WYSIWYG) preview of the actual symbology of the feature. Although the display is semitransparent, it may still obscure the underlying imagery. This is most problematic when digitizing polygons, such as building footprints. To turn off the WYSIWYG feedback, uncheck Use symbolized feature during editing on the Editing Options > General tab. In the following examples, the left graphic shows sketching a building with the symbolized preview enabled, and the right graphic shows it off with the sketch displayed only as a wireframe. When this option is off, it is much easier to see the building you are tracing.

The settings for the edit sketch symbols are stored in the ArcGIS registry, so are available for all your maps. While the sketch is most commonly used for digitizing new features, it is also used when reshaping a feature, cutting a polygon, and so on. Your changes are reflected in those cases as well.

Symbols used with snapping
You can modify the appearance of the snapping pointer and SnapTips symbols by clicking the Snapping menu on the Snapping toolbar, then clicking Options. Note that these settings are stored in the ArcGIS registry and only apply to the Snapping toolbar snapping environment introduced in ArcGIS 10; they are not used in classic snapping, which has no symbology options.

From the Snapping Options dialog box, you can change the color of the snap symbol that indicates whether you are snapping to an edge, end, or other element by clicking the color palette. To see SnapTips better, check the Background box to add a solid fill behind the text so it stands out from the underlying raster. If you want to change the SnapTip font, color, size, or background, click the Text Symbol button to open the Symbol Selector dialog box.

The left graphic shows the SnapTip as it appears by default, but the SnapTip is much more visible in the right graphic with a background and larger font size. Since the snapping elements are semitransparent, you may need to experiment with different colors to find ones that are distinguishable over your imagery.

Layer display settings
In addition to the editing-related settings, changing the appearance of the layers themselves makes it easier to view the image and edit the features on top of it. For example, turning off unnecessary overlapping layers and adding layer transparency can make the raster visible through the features you are editing. This is especially useful when working with polygons, which cover up any underlying layers. You could consider symbolizing polygons with crosshatch patterns rather than solid fills.

To make the raster lighter, use the Image Analysis window to add transparency, increase the brightness, or apply a contrast stretch.

For more information:

Content provided by Rhonda (Editing Team)

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Using ArcMap to create layer packages with 3D point symbols!

OK, so the title is a bit misleading, but we have been hearing from a few of you in regards to getting layer packages to display with 3D points in ArcGIS Explorer, and there is a way to do this using ArcMap.  The quick answer is to use a Layer or Layer Package that already has the desired 3D layer properties. Simply, add a layer with 3D properties to ArcMap and reset the data source for the layer to your point feature data.  While you cannot set 3D properties for a layer in ArcMap, if the layer already has 3D properties, ArcMap does not remove them.

For those of you that know how to reset the data source on a layer in ArcMap, you are set… you just need a point layer that already has 3D properties.  I have made one that has the basic settings for 3D points that most people want and you can get it here. The 3D properties will work well for general visualization of points in 3D and 2D.  A full explanation of the details follows below…

The issue:  points from an ArcGIS Layer appear flat (draped) and are too big in ArcGIS Explorer 3D
For an example we will take a look at a default layer from ArcMap.  In this case I have added point features representing cities in the United States (orange points).  I also have a shaded relief basemap loaded in for reference.

 

If we create a layer package (see help for creating packages) out of this layer and open it in ArcGIS Explorer we will see the following:

 

In ArcGIS Explorer 2D, it looks pretty good.  The layer has 2D properties and ArcGIS Explorer displays it as it is seen in ArcMap.  If we switch to 3D in ArcGIS Explorer we see that the points are displayed in a larger size.

 If we zoom in on the map we also see that the points are too big and they are draped on the surface.

 

This occurs because the layer does not have good 3D properties for this ArcGIS Explorer use case.  Using the layer package referenced above this can be corrected. Open this layer from ArcGIS.com in ArcMap.


 
The layer package contains a single point, but that is not important – because we just want the 3D properties from the layer. You are using this layer as a template for your point data.

Right Click on the layer and open the layer’s properties…


 

 On the Source Tab click the ‘Set data source’ button and browse to your point data.

 

Click OK and see your data displayed with the template layers symbols.  Pictured here is the same cities point data used above.
 

If we create a layer package from this layer and open it in ArcGIS Explorer 3D, it looks like this:

 

The symbols have better sizing for this use case and they display in 3D.
In ArcMap we can adjust the layer properties further, changing the layer name, symbol, symbol renderer, turn on labels, set HTML popup etc…  While 3D marker symbols like those in the ArcGIS_Explorer style work well, you can also use ArcMap’s character marker symbols .  For example, I changed the layer name, chose the ‘Hospital’ symbol from the ESRI style and changed the size from 18 to 14.

In ArcMap it looks like this:

In ArcGIS Explorer 3D it looks like this:

 

If you have a 3D Analyst license you can use the layer as template in ArcGlobe.  Of course, you can also use ArcGlobe to adjust the layers 3D settings and do more advanced 3D display.

Content for this post provided by Mark B. (ArcGIS Explorer Team)

Posted in 3D GIS, Uncategorized | Tagged , , , , , , , , , , | Leave a comment

Using snapping effectively in ArcGIS 10

Snapping allows you to create features that connect to each other so your edits are more accurate, with fewer errors. In ArcGIS 10, you can choose from one of two snapping environments to use when you are editing. The default is the new Snapping toolbar, which is flexible, easy-to-use, and has more snapping types, more options, and better feedback. Alternatively, you can enable classic snapping, which provides fine-grained control over the snapping environment. This post provides an overview of each environment, so you can decide which one allows you to get your editing done most effectively.

Snapping toolbar (the default snapping environment)
The Snapping toolbar is the central location where you manage the snapping settings. There is minimal setup required, since the most common snapping types are enabled by default. The Snapping toolbar environment is used by the editing tools, but is also available outside of an edit session and is used by other parts of ArcGIS, such as georeferencing and the Measure tool. Snapping is also part of ArcGIS Engine, so you can build custom applications that utilize snapping.

Snapping is managed at the map level, so whenever a snap type is turned on, you can snap to any visible feature layer. This also includes layer types that are not editable, such as basemap layers or CAD files. You cannot snap to features that are hidden from the map, though, including when the layer is turned off, has a definition query (visible features in the layer can still be snapped to), and is beyond the layer scale range. Snapping is useful when creating new features or when editing existing ones, such as by reshaping edges, splitting lines or polygons, moving features, or editing features in a topology.

The Snapping toolbar has buttons to enable snapping to points, edges, vertices, and ends, which are all on by default. The order in which snapping occurs to certain types is determined automatically; the highest priority is given to snapping to sketch elements. To turn on or off individual snap types, click them on the toolbar. If you want to stop snapping temporarily, hold down the space-bar. To turn off snapping altogether, uncheck Use Snapping on the Snapping menu.

To set options for working with the ArcGIS 10 snapping environment, click the Snapping menu and click Options. From there, you can set the snapping tolerance in pixels, which is the distance your pointer needs to be from a feature for snapping to occur, or customize the snapping feedback. As you move your mouse pointer, you get visual cues in the form of pop-up SnapTips and the pointer icon to tell you the layer you are snapping to and with which snapping type. You can change the color of the icon and the content, font, and color of SnapTips. When you are working over imagery, add a background to the SnapTip to place a solid fill behind the text so it is easier to read. Your snapping settings apply to all your ArcMap sessions since they are saved in the registry for the application.

Each snapping type (vertex, edge, endpoint, intersection, and so on) has its own pointer icon, which matches the buttons on the Snapping toolbar. For example, the pointer is a square with lines inside it when you are snapping to an endpoint and becomes a box with diagonal lines when you are snapping to an edge. In the following example graphics showing streets and parcels, you can see the SnapTips with the layer name and the snap type. When creating a new road, snap to the existing endpoint (Streets: Endpoint) so the segment connects to it. If you need to create a building footprint at a parcel boundary, snap to the Parcels: Edge.

On the Snapping menu, you can enable snapping to an intersection, segment midpoint, or curve tangent point. These additional snap types are only available with the new snapping environment. For example, intersection snapping allows snapping to locations where two features intersect but there may not be any defined vertex or endpoint there. You might use intersection snapping when you are adding points at street intersections or dividing a feature where it meets another feature. If you need to split a park where a stream crosses it, you can turn on intersection snapping, then select the park polygon, click the Cut Polygons tool on the Editor toolbar, snap to the first intersection, and use Trace to follow along the stream’s edge. When you have traced across the park, snap to the other intersection and finish the sketch to cut the park into two features.

Since you can snap to any visible features in a layer, you may need to spend some time authoring your map. If you find you are snapping to layers you don’t want to snap to, make sure you need that layer to be displayed in the first place. By turning off unnecessary layers, disabling certain snap types, setting layer scale ranges, and making sure your labels and symbols are as descriptive as they can be, you can use the Snapping toolbar more effectively.

Classic snapping
Classic snapping is the snapping environment that you may be familiar with from ArcGIS 9. Classic snapping is available to you in cases where you need more control over the way snapping occurs or if you are working with a part of ArcGIS that uses only classic snapping, such as tracing with the ArcScan for ArcGIS extension and editing in ArcScene and ArcGlobe. When classic snapping is enabled on the Editing Options > General tab, editing tools only use the classic snapping environment. However, georeferencing tools, the Measure tool, and other non editing tools continue to use the snap settings on the Snapping toolbar.

Classic snapping allows you to manage the individual snapping types, layers, and priorities. In classic snapping, snapping settings are specified for each layer and type (vertex, edge, or end) in the Snapping Environment window, which you open by clicking the Editor menu, pointing to Snapping, and clicking Snapping Window. No snapping occurs until you check some boxes in the window. You can drag and drop layers up and down the list to change the snapping order; layers at the top will be snapped to before layers further down the list. To snap to points, check the Vertex box since there is no specific point snap type in classic snapping.

To set options for classic snapping, click the Editor menu, point to Snapping, and click Options. From there, you can change the snapping tolerance in either pixels or map units and turn on SnapTips, which are off by default. SnapTips with classic snapping cannot be customized (they will always show the layer and type) and are opaque yellow, rather than the semitransparent SnapTips available with the Snapping toolbar. The setting for enabling classic snapping is stored in a map document; its options are saved in the ArcGIS registry.

Enabling classic snapping is most useful for complicated maps with lots of overlapping layers. When working with complex utility data, for example, classic snapping may be beneficial because you have many features in one location, but need to snap easily to a particular feature and in a certain order. If you are creating water mains, you could move that layer up in the list so new mains snap to existing mains first and set whether they should snap at vertices, edges, or ends. Since utility data often has many point features, you can reorder the point layers in the list so new lines connect to certain points, such as system valves or hydrants, before they snap to other types of point features. If you do not want to snap to a particular layer at all, uncheck it from the list. However, features not visible because of definition queries can still be snapped to when you are using classic snapping.

This kind of fine management of the snapping environment is only possible with classic snapping. However, this also takes a lot of work to maintain and set up, considering that each layer in the map is listed in the window and has three separate boxes to check. So, if you are trying to snap to a feature but no snapping occurs, you have to sort through a potentially lengthy list of layers and checkboxes to enable the snapping. With the Snapping toolbar, snapping is on for all layers.

Summary
Each snapping environment has trade-offs of ease versus control that you need to evaluate. Some users have reported that they were skeptical of the Snapping toolbar at first and immediately went back to classic snapping because they were familiar with it, but eventually spent time using the Snapping toolbar and loved it. The Snapping toolbar might take some time to get used to, but its simplicity and power should meet the needs of most editing tasks. However, you can switch between the snapping environments at any time on the Editing Options dialog box so you can use the one that is most appropriate for your current work.

Data credits:
Data used in the examples is from the Water Network Utilities Template by Esri and Fort Pierce, Florida.

For more information:
About snapping
About the editing classic snapping environment

Content provided by Rhonda (Editing Team)

Posted in Editing | Tagged , , , , , , | 5 Comments

Free ArcGIS 10 Deployment Training

A series of “how-to” videos is available to help you with the deployment of
ArcGIS 10, including

  • ArcGIS 10 Deployment Quick Tour
  • Customer Care Site: Software Management
  • Customer Care EDN
  • ArcGIS 10
    Download Management
  • Installing ArcGIS Desktop
  • ArcGIS 10 Authorization
  • ArcGIS 10 Deployment Best Practices

The videos are between 10-30 minutes long, and are available through the Esri Training web site.

An Esri Global Account is required.This content is for US customers but will be posting non US information soon.

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Preparing a map for editing: Setting layer properties

To get the most out of editing in ArcGIS 10, use the
Layer Properties dialog box to (1) prepare symbology, (2) simplify attribute
fields, and (3) set a display expression. Doing these things for each layer you
plan to edit can help make your data compilation tasks easier and
straightforward. This post walks you through setting up a parcels land-use
layer so you can create and edit features in it.

Preparing the layer’s symbology

The Layer Properties > Symbology tab allows you to set the symbols
used to draw the layer. Since feature templates are based on the symbols used
in the map, be sure to symbolize your layers appropriately before you start
editing for the first time on a map since ArcMap creates feature templates for
you then, or anytime you create feature templates yourself. If you change the renderer
type after you create feature templates, you will end up with templates that do
not reflect the features you want to create.

When creating features, you should use either the Single Symbol or
Unique Values renderer. If you are symbolizing with unique values, make the
labels for your symbols meaningful, as the symbol labels become the names for
the feature templates. For example, the parcels layer has symbol category
labels taken from the raw attributes of AGR, COM, IND, RES, and UNK, which are
shortened versions of various types of land-uses. Expanding the text of the
symbol labels to Agricultural, Commercial, Industrial, Residential, and Unknown
will reduce the cleanup needed on your feature templates after they are created
and help other editors understand which features they are creating. The symbol
labels are also used in the entries in the table of contents and the map layout
legend, so there are additional reasons to do this. These graphics show the
Layer Properties > Symbology tab and the resulting feature templates in the
Create Features window.

When there is a problem with the symbol for a feature template, the
Template Properties dialog box displays an exclamation point icon in the
preview area. The template is also shown in the Create Features window as a
silver layer icon, rather than the symbol that will be assigned to the new
feature. This often happens when the symbology was changed dramatically after
the feature template was created, such as switching renderers or symbol
categories. If this occurs, look at the feature template’s default attributes
to ensure they match the current symbology or symbol category. You can also
simply delete the template and re-create it to synchronize the symbols.

Simplifying the attribute fields

When you look at your parcels layer in the Attributes
window, by default, all the fields are displayed in their original order and
with their names as they appear in the data source. The field names are hard to
read and understand since they use capital letters and underscores because
spaces are not possible in the actual field names. Fields that you cannot even
edit are displayed, which makes it harder to find the fields you want. This is
a lot of junk content to wade through when you want to edit these attributes! This
layer could benefit from some work on the Layer Properties > Fields tab.

The Fields tab is the central place for you to set up the
display properties of fields. Spending time organizing fields makes your
editing and overall ArcGIS experience more productive because the settings are
used throughout ArcMap, including in the attributes table, the Attributes
window, and the Identify window. In addition, they are maintained when you
share layers with others through layer files, layer packages, map packages, and
Web services.

The left side of the Fields tab contains a list of all
the fields in the feature class or table, including any fields that have been
joined to it. If you have a long list of fields but only plan to edit the
attribute values for a few fields, hide the ones you do not need to by
unchecking them in the list. For the parcels layer, you might be only
interested in seeing information about the land-uses and the IDs, so you can turn
off nearly everything else. To save even more space, hide system fields that
ArcGIS does not allow you to edit anyway, such as the Object ID, Shape, Shape_Length,
and Shape_Area. This does not delete the fields; it simply turns them off to
make it easier to access the fields you want. Many dialog boxes have option
buttons that allow you to view all fields in a layer if you need to see them
again temporarily.

The order of the fields list is the default order in
which they are displayed throughout ArcMap. You can change the order to promote
to the top of the list the fields you use most often. To reorder a field, click
it in the list and drag it to the position you want, or click the arrow buttons
to move it up or down the list. You can also select multiple fields and reorder
them at the same time. With the parcels layer, move up the IDs and land-use
code fields since you plan to edit them.

When you click a field in the list on the left, the individual field’s properties are displayed on the right side of the tab (the
right side will be blank when you have multiple fields selected). You can change
the properties that are shown in the Appearance section, which specify how the
contents of the field are displayed in ArcMap, but not the system information
under Field Details. When you click a row on the right side, an explanation of
the property is provided in the box at the bottom of the tab.

In the Appearance section, you should give your fields
aliases to specify an alternate field name that is descriptive and user-friendly.
Field aliases do not have to adhere to geodatabase naming conventions, so
aliases can have spaces between words or be as long as necessary. For example, for
the field, “LAND_USE,” set the field alias as, “Type of land-use.” The alias is
a lot simpler to read and understand than the source field name.

You can also set a field to be read-only, which means you
can view but cannot edit that field, regardless of the file or database
permissions. This is useful when you need to see the value of a field for
context, but do not want to inadvertently update its value. If you want to
distinguish certain fields-for example, to make them easier to see when editing
in the Attributes window-set the Highlight property to Yes. This will add
background shading so those fields will stand out from the others.

After a little cleanup, the list is a lot easier to
manage and edit. Only the most useful fields are shown, with clearer alias
names and a more appropriate order.

Two of the most popular requests on the ArcGIS Ideas site, where you can submit and
vote for ArcGIS software enhancements, are the ability to rename fields and
reorder them after they have been created. Although this functionality may not
be available in the underlying database, you can get the same result by
authoring your map and setting the field properties.

You should follow these guidelines when working with
stand-alone tables, since the field properties are used with tables, too. If
you create a relationship class to relate a table of landowner information to
the parcel layer, you can navigate through the related records to edit the
landowner table in the Attributes window. If you turn off unwanted fields, reorder
fields, and set other properties in the landowner table, it will be easier to find
and edit the table’s values, too.

Setting the display expression

The display expression is new with ArcGIS 10 and is found
on the Layer Properties > Display tab. Setting the display expression
ensures that the most useful information is displayed when representing a
feature in the Attributes window, the Identify window, in HTML Pop-ups, and
other places across ArcGIS. The display expression can simply be the contents of
a field by itself, which is similar to the primary display field from previous
releases. However, the display expression is more powerful because you can
customize the text. This allows you to enter your own text or combine the
contents of multiple fields. For example, you could write an expression that
would include the text, “Land-use type:” before the field value. This would be
entered on the Display Expression dialog box as, “Land-use type: ” + [Land-use
field name].

 

When editing, the display expression makes it easier to
navigate the Attributes window tree. Stand-alone tables have a display
expression property, so setting it on the table can help when viewing related
records, too. The display expression is also shown in the Edit tool selection
chip, which is a small pop-up that appears on-screen to help you select the correct feature when you click multiple overlapping features with the Edit
tool. For example, you are trying to select a road that overlaps a parcel
polygon. If you click the road, the selection chip appears, allowing you to
choose whether to you want to select the road line or the parcel polygon.

Content provided by Rhonda (Editing Team)

Posted in Editing | Tagged , , , , , | 1 Comment

Sign Up for a Free ArcGIS 10 Seminar

Learn practical ways to enhance analysis, access imagery, make better use of the Web, and apply ArcGIS in the field at Esri’s free seminar, Increase Productivity with ArcGIS 10 . All industry professionals are invited to this event, which will be held in 74 U.S. cities from September to November 2010. Register to attend at a location near you.

 

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Esri Mid-Atlantic Water/Wastewater Special Interest Group

We’ve created a LinkedIn Group for the Esri Mid-Atlantic Water/Wastewater Special Interest Group so we can share more details about our first meeting and answer any questions.  Here is a link to the group – http://linkd.in/bum9lz

Going forward we’ll be using this LinkedIn group to plan future SIG meetings and hope it becomes a useful forum for water, wastewater and stormwater ArcGIS users in the Mid-Atlantic region.

As we’ve previously announced, the SIG’s first meeting is at the ESRI Mid-Atlantic User Group Conference December 1st in Philadelphia, PA. More information about the MUG Conference and the SIG can be found here – http://bit.ly/bZGvCX

We’d also like to announce that we’ve selected our first user presentation for the December 1st SIG meeting.  Joe Spollen will be presenting on “A Day in the Life of a Water Company GIS Analyst”.  During this presentation Joe will share his experience using ArcGIS Desktop and Server applications at a large private water utility to maintain water distribution system data, create and share maps, support capital planning and other common daily tasks for water utility GIS users.

We’ll be sharing more of the agenda as we confirm other user presentations.

Posted in Water Utilities | Tagged , , , , , , , , , | Leave a comment

Preparing a map for editing: Assembling the data to edit

It’s a good idea to spend a little time preparing your map for editing. You’ll be a lot more productive and save clicks if you set up your map and data before you really get in and make edits. This post is part of a series on the subject.

Choosing where to store your data
ArcGIS allows you to create and edit several kinds of data. You can edit feature data stored in geodatabases and shapefiles, as well as various tabular formats. When gathering your data in preparation for a geographic information system (GIS) project, make sure all the data you want to edit is stored in the same workspace, which is a single geodatabase or a folder of shapefiles, since you can only edit one workspace at a time. If you are still using shapefiles, consider migrating to a geodatabase, such as a file geodatabase, which provides more functionality and storage capacity with as much speed and simplicity as shapefiles. You can use the geoprocessing tools for importing and exporting data, as well as often simply copying and pasting feature classes in the Catalog tree, to get data into a geodatabase.
With the Catalog window now embedded in ArcMap, you can perform data management tasks and access your data without having to open the separate ArcCatalog application. This is useful in itself, but a few additional settings can make your use of the Catalog window even more productive. For example, the directory where you save a map document is tagged as the Home location and is always promoted to the top of the Catalog window when that map is open. Therefore, if you put the geodatabase in the same folder as the map document you are working on, you can quickly find your data in the Home location without having to navigate through the whole folder tree. Doing this also keeps your GIS project better organized since all the data, maps, and other supporting materials are in the same place. In addition, you can set your geodatabase as the map’s default geodatabase (right-click it in the Catalog window and click Make Default Geodatabase) so any outputs will be saved in that location automatically.

Choosing the projection for your data
As you compile your data, you need to consider the projections. First, you should make sure the feature classes that you will be editing all have the same coordinate system. In addition, if you have data in a geographic coordinate system, you may want to change to an appropriate local projection. This will improve accuracy when editing and make it easier to enter lengths and other measurements since values are specified in the map units of the coordinate system by default. For example, if your map uses the geographic coordinate system of WGS 1984, when you are editing, ArcMap interprets any entered values as decimal degrees because those are the map units for that coordinate system. So when you type 100 for the length of a segment, as shown below, ArcMap interprets that as 100 degrees and will likely present you with a series of error messages. On the other hand, with a projected coordinate system, the map units will be in a more useful unit, such as meters or feet. Also, a projected coordinate system is flexible because it allows you to specify distances in units other than the map units by including an abbreviation with the value; you can only enter values in the coordinate system’s map units (typically, decimal degrees, as just discussed) when working with a geographic coordinate system.

The coordinate systems of the layers also need to match the coordinate system of the data frame. If the coordinate systems of the data frame and layers are different, the layers will be projected on the fly to the coordinate system of the data frame. Projecting on the fly can be problematic because it may cause unexpected alignment issues when making edits. For example, when editing, you may digitize some lines that look like they connect to other lines. While the lines appear to be snapped to edges when projecting on the fly, the lines may be dangling when you display them in their native projection. In addition, you cannot perform shared editing of coincident features through a map topology for layers that are being projected on the fly. 

To avoid all these issues, make sure you are not projecting on the fly while editing. When you have an empty data frame, it automatically takes on the coordinate system of the first layer added to it. To change the data frame’s coordinate system, right-click the data frame name in the table of contents, click Properties, then click the Coordinate System tab. In the Select a coordinate system box, you can quickly set the coordinate system of the data frame to match that of a layer in it by clicking the Layers folder and navigating to the coordinate system listed underneath one of the layer names. Since the coordinate system of the data frame and the layers will now match, the layers will not be projected on the fly.

Starting an edit session
When you are finally ready to edit your data, turn on the Editor toolbar (if it’s not already displayed), click the Editor menu, then click Start Editing. This begins an edit session, which you will end when you are done. When you start an edit session on a geodatabase workspace, you have the ability to edit all the feature classes and tables in that geodatabase at the same time. With an edit session on a shapefile folder workspace, you can edit all the shapefiles that are stored in that directory.
If you start editing in a map that contains data from more than one workspace, you are prompted to choose the workspace you want to edit. On the dialog box, click a layer at the top to select its workspace source at the bottom of the window (notice that the database symbols change color), or click a workspace at the bottom of the window to view the layers in it at the top. Once you have picked the workspace, click OK to start the edit session. Later, if you need to edit data in the other workspace, stop editing, then start a new edit session and choose that workspace. Keep in mind that you can also right-click a layer in the table of contents, point to Edit Features, then click Start Editing, which automatically starts an edit session on the entire workspace containing that layer.

Once you choose the workspace to edit, sometimes you may see another dialog box appear about problems that ArcMap encountered when you started editing. This dialog box will list the layers that are being projected on the fly, as well as any other issues such as missing licensing, layers that cannot be edited because they are read-only or inside a basemap layer, and so on. You can double-click each message to open a help topic with more information.

For more on the Catalog window, projection considerations, and edit sessions in ArcGIS 10, see the following:
What’s new for accessing your data in ArcGIS 10
About editing data in a different projection (projecting on the fly)
About edit sessions

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Data Precision vs. Map Scale

The trend in the water and sewer industry is for utilities to capture and maintain in GIS more detailed information about their utility networks at a higher level of precision. 

Yet most water utilities are still trying to display all of this increasingly detailed data using the same paper map products they’ve historically used, particularly for use in the field.

Simply put – it ain’t easy to get all of the data in your geodatabase onto paper field maps using the same scale and map grid that your utility has always used.  Continue reading

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