Tag Archives: ArcGIS 10
Overviews and pyramids: Part 1 of 2, What are they and why do I need them?
This is part 1 in a 2-part blog. Part 1 provides an overview of pyramids and overviews. Part 2 will provide you with some guidance on generating them when creating a mosaic dataset.
Basically—overviews are not pyramids and pyramids are not overviews. But pyramids generated by ArcGIS have an .ovr extension (short for overview)…Wait, did I just write that?
Yes, the storage format for a pyramid is an .ovr file. But please don’t confuse this with overviews. Fortunately, overviews are organized in a folder named *.overviews. Both are similar but pyramids are created for raster datasets and overviews are created for mosaic datasets.
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Pyramids |
Overviews |
Description |
Lower resolution (downsampled) images of the original data. |
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Purpose |
Improve display speed and performance. |
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Created for |
Raster datasets |
Mosaic datasets |
Format |
Writes .ovr files—with a few exceptions. |
Writes as .tif files. |
Reads pyramids stored externally as *.ovr or *.rrd or internally (e.g. MrSID) |
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Storage |
In a single file that generally resides next to the source raster dataset and using the same name. |
By default, in a folder next to the geodatabase with a *.overviews extension, or internally for ArcSDE.Storage location is customizable. |
Storage size |
2 to 10% (compared to original raster datasets) |
|
Downsampling factor |
2 |
3 (default) |
Extent |
|
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Options when building |
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Why are you generating them?
Pyramids aren’t mandatory—but without them, the display speed of your raster dataset can be prohibitively slow, especially if the datasets are very large.
Overviews aren’t mandatory—but they are highly recommended. You do not have to create them or you can generate them in only particular parts of the mosaic dataset, such as a highly visited part of the imagery. However, if you don’t create them you may not see any imagery (you may see a wireframe instead or gray images), since there is a limit to the number of rasters that will be processed at one time (which you can change). Without them, the mosaic dataset may display slowly because of all the processing.
How to create pyramids
If a raster dataset doesn’t have pyramids, then you will often be prompted to create them when you display the data in an ArcGIS application, such as ArcMap. But it’s better to create them before you use the data. Pyramids can be created using geoprocessing tools. There are a few tool choices, since it depends on whether you have one or many datasets to process. To learn about these, see Building pyramids using geoprocessing tools. You can change the properties of the pyramids, such as the resampling method and compression via the geoprocessing environments.
How to create overviews
To create overviews, first they are defined, then generated. When they are defined, the application analyzes the mosaic dataset and using the parameters set for the overviews it defines how many are needed, at what levels, and where. Then they are added as items in the mosaic dataset which appear as new rows in the attribute table. At this point, only the rows have been created to identify the properties and number of the overviews. Next, the overview files are generated. Both defining and generating can be done with one tool—Build Overviews. However, if you need to modify any properties, such as defining a new output location or tile size, then you must run Define Overvews first (to define the properties and add the items to the attribute table), then run Build Overviews to generate the overview files.
When you do generate them, the mosaic dataset keeps track of any changes made to it, such as updating an image, adding or removing images, or altering the footprints. By running the Build Overviews tool or Synchronize Mosaic Dataset tool, with the appropriate options, the overviews will be updated.
Associated blogs
- Oh where oh where have my pyramid files gone?
- Pyramids and overviews, or pyramids or overviews?
- Take a look at raster compression, pyramids, time, and space
Submitted by: Melanie Harlow
Expanding the power of the Attribute Assistant
Here at Esri, we always try to help one another out. Well the Local Government team asked if we could expand the functionality of the Attribute Assistant and make a series of construction tools to help with address data management workflows; and we obliged. We came up with some pretty cool new rules for the attribute assistant and some interesting construction tools that will be used to streamline address maintenance workflows. Even though these have been designed for managing address information, you may find them very helpful. Let’s first take a look at these new attribute assistant rules.
The first rule we needed to create was CASCADE_ATTRIBUTE. This rule will allow you to make a change to an attribute in a table or layer and push that new attribute value to every feature that contains the value. So in the address world, we have implemented a Master Street Name table. Say a road was renamed, we can go into the table, change the road name, and the rule will open up the Road Centerline layer and make that change to every road with the old name, then open up the Site Address Point Layer and update the road name as well. Pretty cool, huh?
The second rule we created was VALIDATE_ATTRIBUTE_LOOKUP. This rule will validate an attribute change against a look up table or layer. Let’s look out how you would use this in address land. If I created a new road and I want to make sure the road name matches a road in the Master Street Name table, I can set this rule up to monitor my Street Name field and check that value against the Master Street Name table. The cool thing about this rule is all I have to do is enter a piece of the road information. If it finds more than one record in the street name table, it presents a prompt, where you can select any of the matching values. How is that for data validation?
I also mentioned we are working on some new construction tools. These are still in development, but here is what we are working towards. One tool will allow the user to click a reference point, in our case, an address point that represents the location on the centerline of which the address is derived, create this point if it does not exist, then create a series of site address points with information from that reference point or the centerline underneath it. So basically, you can create a series of points all with information from source point. The second is a tool to draw a new road and split any intersecting roads and prorate their address information.
If you want to try the new rules out, as well as a few other enhancements, we have posted a beta of the tools on the forum.
Thanks
Mike from the Water Team
Raster XML file contains a histogram in ArcGIS 10
At 10.0, ArcGIS began storing the histogram for a raster
dataset when it generates the statistics. This allows the application to
provide more capabilities, such as adding stretches, like Percent Clip. If you export the statistics file you can take a look all
the information.
Previously to 10.0 the exported XML file would look like…
<?xml version=”1.0″?>
<RasterStatistics xml:lang=”en”>
<DatasetName>dem30</DatasetName>
<Band Name=”dem30″>
<min>2081</min>
<max>3447</max>
<mean>2544.409567056246</mean>
<stddev>208.6604762988481</stddev>
</Band>
</RasterStatistics>
At 10.0 the exported XML file will contain the histogram…
<?xml version=”1.0″?>
<RasterStatistics xml:lang=”en”>
<DatasetName>dem30</DatasetName>
<Band Name=”dem30″>
<min>2081</min>
<max>3447</max>
<mean>2544.409567056246</mean>
<stddev>208.6604762988481</stddev>
<Histogram>
<npixels>2597680</npixels>
<min>2081</min>
<max>3447</max>
<v>23</v>
<v>45</v>
<v>54</v>
. . .
</Histogram>
</Band>
</RasterStatistics>
Submitted by: Melanie Harlow
ArcGIS 10 (Desktop, Engine, Server) Service Pack 3
ArcGIS
10.0 Service Pack 3 is now available to download via the ArcGIS
Resource Center
Here is the link to SP 3 for ArcGIS 10 (Desktop, Engine, Server)
New ArcGIS Online Basemaps
A couple of nice additions to the ArcGIS for Desktop 10 basemap gallery were made last week:
1. We added an entry for the new Light Gray Canvas basemap which provides a neutral basemap that makes your thematic data really stand out. There are some useful blog posts about this new basemap on the Mapping Center blog
2. We renamed the ‘Physical’ basemap to ‘Physical and Ocean’ and added the Ocean basemap
into this as a layer. When you add the Physical and Ocean basemap into
your map, you can turn the Ocean basemap on in the entry for this
basemap in the Table Of Contents if you want to see rich detail for the
world’s oceans.
To add these basemaps into ArcGIS for Desktop 10, choose File > Add
Data > Add Basemap in ArcMap or ArcGlobe. To add them into 9.3 or
9.3.1, choose File > Add Data From ArcGIS Online.
Alternatively, here are the layer packages for the Light Gray Canvas basemap and the Physical and Ocean basemap that you can add directly into your map or globe.
To add these basemaps into your map or globe via the Catalog, make a connection to this ArcGIS server: http://services.arcgisonline.com/arcgis/services
and then add the World_Light_Gray_Base and World_Light_Gray_Reference
services from the Canvas folder, or the Ocean_Basemap service.
New Light Gray Canvas Basemap
A couple of nice additions to the ArcGIS basemap gallery were made last week. For more information checkout this post on the new Light Gray Canvas basemap on the Mapping Center blog.
Here’s a post on the Desktop blog with more information on accessing the new basemap in ArcMap
Orthorectification: To Geoid or not to Geoid
When you ortho-rectify a raster dataset, you are given a choice whether or not to use Geoid correction. Geoid correction should be applied when your data source is using orthometric heights and you want to perform a geoid (EGM96) correction to the z-values. Orthometric heights are measured near sea level – which tends to be the case in many images.
Orthorectification can be performed various ways within ArcGIS:
- Geoprocessing – Create Ortho Corrected Raster Dataset tool
- Image Analysis window – Orthorectify button
- Geomtric Function
- Layer Properties Display tab
Clipping an image or raster in ArcGIS
There are many ways to clip out a part of an image or raster in ArcGIS. What you choose may depend on what you’re doing. For example, if you’re using ArcMap and have a graphic, you can use the Clip button on the Image Analysis window. Or if you want to clip something as part of an automated process you can write a script or model that uses the Clip tool. Continue reading
Fresh additions to the ArcGIS.com Editing Labs group
After hearing your feedback at the 2011 Esri International
User Conference, we on the Editing development team have been busy resolving
some of the workflow issues reported with ArcGIS 10. At your request, we have
developed two new tools for creating smooth curves and another one to cut
circular holes in polygons. You can download these tools from our ArcGIS.com
group called Editing
Labs, which we use as a repository for prototypes and samples to extend the
ArcGIS 10 editing environment (make sure to filter by Show: All Content at the
top of the page). This blog entry highlights the new add-ins available from
Editing Labs.
Curved Construction
Tool
ArcSketch was a free add-on for ArcGIS 9 to support “back of
the napkin,” GeoDesign-style workflows, such as redlining features and
sketching land-use plans. Features could be created quickly by picking a symbol
on a palette, choosing a tool, and clicking the map to draw it. ArcSketch was deprecated
at ArcGIS 10 when this symbol-based feature creation workflow was incorporated
into the core editing experience through feature templates and the Create
Features window.
A user we spoke to at the UC wants to map zones for receiving
aircraft navigation radio signals by connecting known points with smooth
curves. In ArcGIS 9, he used the Curved Polygon tool in ArcSketch to draw these
features, but we were left scratching our heads about how to perform this task as
easily using the construction tools available in ArcGIS 10. So, we got to work
building a new sample for Editing Labs called the Curved Construction Tool.
Once I download and install the Curved
Construction Tool, the Curved tool appears in the tools list on the Create
Features window when I activate a line or a polygon feature template. The
Curved tool allows me to create lines and polygons with curves that are splined
through fixed points. In my case, I am going to use the Curved tool to connect
points representing water sampling locations at springs (shown by the blue
circles on the map) to draw a polygon of a hydrologic study area.
I start the curved feature with a single click and add
subsequent points with clicks. I can utilize the snapping environment to snap
to the existing sampling point features when setting the locations through
which the curve passes. After I have digitized all the curves, I finish the
sketch. When creating polygon features, they are closed automatically with a
curved segment.
Each location I click becomes a vertex shared by adjacent Bézier
curves. The curve is defined by the locations of those vertices and additional
control points at the end of blue Bézier handles that radiate from each vertex.
If I want to reshape or move the curves manually, I can double-click the
polygon with the Edit tool.
Auto Complete
Freehand Tool
Several users told us they want to use freehand shapes to
create adjoining polygons. For example, members of a wildland search and rescue
group need to draw search areas and add adjacent polygons as the search
expands. The existing Auto Complete Polygon tool appends new polygons next to
existing ones, but the editor has to click to place each vertex. The Freehand
tool, on the other hand, creates smooth curves that follow movements of the
mouse without needing to click to create vertices, but the tool does not append
to existing polygons. Therefore, we developed the new Auto Complete Freehand
tool to combine the functionality of these tools.
As with the other sample, once I download and install the Auto
Complete Freehand Tool, the new tool appears in the Create Features window
when I activate a polygon feature template. I am going to use the tool to
digitize adjoining polygons representing vegetation types by tracing over a
basemap image. Starting from the boundary of an existing polygon in the same
vegetation layer, I click once to start the freehand line. I do not need to
hold down the mouse button as I am creating the new polygon’s shape. The new
polygon’s boundary follows the movements of my pointer, although I can hold
down the spacebar if I need to snap to an existing feature.
The new polygon’s boundary must cross or touch the existing
polygon edge at least two times. I just
need to click once to finish drawing the freehand shape and create the feature.
The freehand line is automatically smoothed into Bézier curves, although the
existing segments that are shared with the new feature are not smoothed. The
vegetation polygons now share a border, but the Auto Complete Freehand tool
allows me to avoid digitizing that edge twice or creating overlaps or gaps
between polygons.
Cut Polygons With
Circle Tool
We heard from a couple of users who want to cut a polygon
with the shape of a circle. For example, one user works with farmlands that are
irrigated by center-pivot systems and needs to cut out the circular-shaped
fields from the surrounding acreage. Another user edits circular oil tanks and
wells that should be cut from the well pad features. These users had found a
simple way of doing their tasks in ArcGIS 9, but ArcGIS 10 requires two steps: drawing
a circle feature and using the Editor menu > Clip command to cut out the
circle. In addition, Clip is inadvertently causing them to edit more features
than intended, since it cuts all visible and selectable polygons underneath the
selected feature. After hearing these scenarios, we created the Cut Polygons
With Circle Tool add-in for Editing Labs so these tasks could be performed
easier in ArcGIS 10.
Using the example of center-pivot irrigation fields, I am
going to cut out actively growing crops from the surrounding perimeters.
Center-pivot is a form of crop irrigation in which equipment rotates around a
hub, creating a circular pattern of irrigated cropland that is often visible in
aerial photography. Once I install the Cut
Polygons With Circle Tool add-in, I need to open the Customize dialog box
in ArcMap and drag the command onto a toolbar, such as the Editor toolbar.
Next, I select the agricultural field and click the Cut
Polygons With Circle tool on the toolbar to which I added it. Using the imagery
as a guide, I click to place the center of the circle at the field’s central
pivot point. I could have also used the A key to enter x,y coordinates for the
center point. A line representing the radius appears inside the circle as I
draw it. I can drag the circle manually, or since I know that the radius of the
field is 200 meters, I can press R and type the value.
After entering the radius, I press ENTER to finish the
circle and cut the polygon. This leaves me with two features: the outer perimeter
that now is a multipart feature with a hole in it and the inner circle. Since
the circle represents the actively irrigated crop area, I update the feature’s attributes
now that it has a land-use type different from the surrounding field.
Giving us feedback
Please let us know what you think of these tools by adding a
comment to their download pages. We have been uploading samples to Editing Labs
regularly, so check back for new additions. When accessing the Editing Labs
group, make sure to filter by Show: All Content at the top of the page. You can
submit general suggestions on how we can improve the editing experience by adding
to the ArcGIS Ideas site or contacting Esri Support. In addition, we encourage
you to join the ArcGIS 10.1 beta
program to preview and provide feedback on the next release of ArcGIS.
Special thanks to the UC attendees who spent time helping us
understand their needs.
Post from Rhonda G. (Editing Team)
Welcome Esri Support to the ArcGIS for Local Government Team
When the ArcGIS for Local Government program began nearly three years ago with a set of maps and apps for water utilities, the user base was relatively small and the processes for receiving technical assistance with the maps and apps were still being formulated. Users with questions regarding the maps and apps typically contacted members of the local government, water utilities, land records or public safety teams themselves, either directly or through the email alias. Team members did their best to address questions from users but with more than 50 maps and apps on the Resource Center today, and almost 50,000 downloads to date, it is difficult to meet everyone’s needs.
Today, ArcGIS for Local Government requires a support solution that can keep pace with our growing user community and deliver the assistance they need. That solution is Esri Support.
Starting today, Esri Support should be the first place ArcGIS for Local Government users in the U.S. go with questions or technical problems related to the maps and apps provided on the Resource Center. From the Esri Support page you can access all of our online support resources like the help, knowledge base, forums, and blogs. In addition, users on software maintenance are able to contact Support by phone, email and even chat. Once Support is contacted, a qualified Analyst will log an incident into our support system and assist the user in troubleshooting the issue until it is resolved. Examples of possible support incidents range from problems with publishing map service, to registering an ArcGIS Add-in, or best practices for loading data in to the Local Government Information Model.
By including Esri Support as the primary contact for ArcGIS for Local Government issues, we gain several benefits, including:
- Greater accessibility – With Support Centers available from 5 am to 5 pm Pacific and a variety of ways to contact them, ArcGIS for Local Government users can now get their questions answered sooner and in a way that is most convenient for them.
- Better transparency – Any incidents logged through Support can be tracked through the My Support, as well as the Customer Care Portal, providing the user with the latest information on the progress being made to resolve the incident.
- Bug tracking – If a user discovers a bug (such as an error in one of the apps or problem with one of the maps) they can log it with Support and keep track of it as it is resolved.
- Better self-help resources – With incidents and bugs on ArcGIS for Local Government maps and apps now being logged into our Support system, users can choose to search our Support resources themselves, often finding the answers they need without contacting a Support Analyst.
- Consistency – Now, when ArcGIS for Local Government team members have questions about technical aspects of the program, they can seek help from the same place they go for their other ArcGIS questions – Esri Support.
These advantages, as well as others, make Esri Support a valuable partner for the ArcGIS for Local Government team. Of course we hope that your experience with the maps and apps is smooth and problem free. But if trouble does occur, it’s nice to know that Esri Support will be able to help you out.
We think our water utilities, public safety, land records, elections, planning, and public works users will find this support model very exciting. So, don’t hesitate to take advantage of all our available online support resources or to contact Esri Technical Support with your technical questions. As always continue to contact us directly if you’d like to learn more about ArcGIS for Local Government and the maps and apps contained in each module.
