Category: Mapping

Symbolize polygon feature as points

Question: We have a building (polygon) layer and I have symbolized the polygon features using point symbols based on the caption field. If I make a selection of this feature and “create layer from selected”, or export the feature the result is again a polygon, but the symbol properties are only always polygon choices. I cannot for the world imagine what I may have done to be able to symbolize the polygons as points. If I change the symbology in any way the feature reverts somehow and can only be symbolized as a polygon???

How did I do this and more importantly how can I recreate it?

Thanks so much

Answer: Given the phrasing you used, I’m going to first differentiate between symbols, data, and layers, to ensure my explanation has better likelihood of making sense.  First there are three basic kinds of vector features, points, lines, & polygons.  In ArcGIS the symbology methods follow suit, marker symbols, line symbols and fill symbols. The symbols are not stored as data (cartographic representation symbology is the exception to that, but I’ll leave that out of this discussion for simplicity’s sake).  A symbol is used to draw a vector feature’s geometry, but only the symbol type that corresponds to the geometry type.  In ArcGIS layers are a way to store the assignment of symbols for a given feature class; and layers are stored inside Map Documents (.mxd) and Layer Files (.lyr).

So, I’m not exactly certain of how you created the enclosed image–it’s possible to do so with a marker fill, but depending on the size of the polygon the marker may not draw, it’s possible to use cartographic representation symbology to do a better job, and it’s also possible to label polygons with a marker symbol.  These methods all represent more work for you to both perform, and to explain to others.

The best option and easiest is to use the Feature to Point tool which will create a (centroid) for each polygon, and include the attributes you need to symbolize the points.  This requires and ArcInfo license.  Then you can just use a marker symbol for the resulting points. This is the least amount of work for not just you, but also your organization.

If you don’t have an ArcInfo license, you can instead use the Calculate Geometry tool in ArcMap to calculate the X and Y centroid coordinates for each polygon–you will need to add two new fields [type = floating point or double] to your buildings, one for the X coordinate and one for the Y coordinate.  Then in ArcMap open the table and right click on each field’s name, and choose Calculate Geometry.

Once you have those two fields, you can use the Add X Y data tool (on the tools menu in ArcMap) to create a point dataset.

Attachment: screen shot

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Symbolizing the hillshade for the World Topographic map

By Charlie Frye, Esri Chief Cartographer

Symbolizing the Hillshade thumb

One of the things I promised myself that I would do last summer was write about some of the key design solutions used in the World Topographic Base Map. Our symbolization of the hillshade is one of the design characteristics that most distinguishes this map. The design intent was two-fold: 1) show shading similar to how hachures were used on hand-drawn maps [to see what I mean one of my favorite 18th century maps depicting the Battle of Bunker or properly Breeds Hill is a good example], and 2) display the low slope areas in white because this creates a ”non-competitive” background for data that is mashed up on this base map. Continue reading

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Using the Buffer tool in ArcToolbox (and comparing with the Buffer Wizard in ArcMap)

By Margaret Maher, Esri Support Services Specialist

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In this blog entry, I discuss using the Buffer Tool in ArcToolbox. I also compare the ArcToolbox Buffer Tool with the Buffer Wizard in ArcMap.  The Buffer Tool, located in ArcToolbox > Analysis Tools > Proximity toolbox uses different methods to calculate buffers. The method used by the tool depends on the type of feature being buffered.

An important thing to understand is that when creating buffers for line and polygon features, the Buffer Tool in ArcToolbox uses the coordinate system of the data being buffered by default. When points are being buffered, another method is used which will be described later in this article. Continue reading

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Symbolizing trees in ArcGIS: Assigning each species a different symbol

By Mamata Akella, Esri Design Cartographer

Tree thumb

Tree symbols are a great way to enhance the appearance of a large scale, detailed map. To make attractive point symbols for trees, you need a good place to start from and thankfully all of us ArcGIS users have that. Using multi-layer character marker symbols, the variety of tree symbols you can create is endless. This blog is meant to introduce (or reintroduce) you to the Esri US Forestry 2 font. It is also meant to give you some tips for creating a variety of tree symbols to use on your maps. Continue reading

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Announcing the ArcGIS Data blog

By Charlie Frye, Esri Chief Cartographer

Data Blog - Thumbnail

September and October sure went fast. We on the Mapping Center team have been very busy working on mapping projects, and have not spent as much time here–but we’re finding a balance and will be getting more good blogs done soon (several are in the pipeline). Continue reading

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Question: Is there a UTM in units of feet for UTM zone 14?

Answer: UTM is always in meters so there will NOT be a UTM feet projection out there.  If you really need to see your UTM data IN feet, then you can follow these instructions to change the units. Essentially, you will reproject the data to a new UTM coordinate system and modify it so that it uses feet instead of meters.

To do this, use the Project tool.  Keep the Output Coordinate System the same as your current UTM coordinate system.  Once you have selected the coordinate system click the Modify button in the Spatial Reference Properties window and under the section titled Linear Unit for the drop-down Name, select either Foot (for international feet) or Foot_US (for US survey feet).

Formerly a Mapping Center Ask a Cartographer  Q & A.

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Globe locator map

By Aileen Buckley, Mapping Center Lead

World from Space Thumb

Need to add a quick locator map to your page layout? Want to spice things up a bit? Try this locator map – it has visual appeal because of the 3D appearance (promoted by the choice of projection and the gradient fill). There are just a few basic steps to creating this map: 1) Prepare the data to make the map, 2) create the map, 3) add your area of interest (optional), and 4) export the data used to make the map, if desired (this will save some drawing time for you.) Continue reading

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Make a map of Washington Elevation–or a similar map for somewhere else!

By Mamata Akella, Esri Design Cartographer

Washington Elevation Thumb

One of the presentations we gave at this year’s User Conference was “The One Minute Cartographer”. While we were developing the presentation, we had several intentions in mind. Most importantly, we wanted to demonstrate to the attendees of our session that making a good map in ArcGIS isn’t always as hard as it seems – often times, it is just a matter of going one or two steps beyond the defaults. Another thing that was really important to us was to make sure that all the data we used to produce this map was also available to you, so we used data on the Esri Data and Maps DVD. In addition, we wanted to create a set of resources with great potential to help map makers in a variety of ways.

Continue reading

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Summarize Raster Statistics according to polygon boundaries

Question: I have a raster elevation file and a polygon SHP file, and I would like to know the mean elevation according to each spatial unit in my SHP file. I see that this can be done through zonal statistics, but I don’t have zones in my raster file, but rather only a SHP file. Later I will repeat the same process for aspect, and slope.

Thank you for your help.

Answer: You should be able to use the Polygon to Raster tool (ArcInfo License) to convert your shapefile to a raster.  One of the tool parameters is the value field from your polygons that will contain the zone ID.  The one thing to watch out for are multipart polygons which will not work, so you may need to use the Multipart to Singlepart tool first.

Though it may be more useful to use the Raster to Point tool.  This will take longer, but then you can use the Identity tool to assign the polygon IDs to these points. That will allow you to do a more meaningful presentation of what average elevation means by including a standard deviation, and a cell count.  To do that use the Summary Statistics tool.  You could get the same information with rasters, though you’d have to produce three raster datasets, and optionally use the Combine tool to have a similar attribute table for a single raster dataset.

Formerly a Mapping Center Ask a Cartographer  Q & A.

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How to use Geologic Mapping Template symbology with your database schema

By Janel Day, Esri Cartographic Product Engineer

Geologic Mapping Template - Thumbnail

A common question we receive goes something like, ‘How can I use symbols from the Geologic Mapping Template with my database?’  The solution is simple, once you have downloaded the geologic mapping template, follow these steps to add its representation symbology to your geodatabase: Continue reading

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