Archive For The “ArcGIS” Category

Full Color Shaded Relief

Contour maps have essentially gone out of fashion, replaced by shaded relief. There are still plenty of uses for contours, but they just don’t look as cool as a well-drawn hillshade. A colored hillshade is even more exciting. Traditionally, the easiest way to do that in ArcGIS was to place a color stretched DEM over [...]

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Sun Glints in ArcMap

Aileen Buckley, at the ESRI Mapping Center, has released a new tutorial on creating what she calls “sun glints”.  These are the reflective glows you sometimes see on water bodies in aerial photographs.  In essence, it’s a tutorial on creating gradient fills in ArcMap – a neat effect that cartographers don’t get to use very [...]

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Typecasting with Field Calculator

One of the keys to good database planning is correctly anticipating what type of data each field will hold.  If a field is expected to only hold integers, it is best to make it an integer field instead of a float or double field.  Doing so will save space and time, and the database structure [...]

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A Difference of Projections

If you divide your time between ArcGIS and QGIS, you may have noticed that they don’t use the exact same projections.  For Northern Colorado, for example, ArcGIS offers “NAD 1983 HARN StatePlane Colorado North FIPS 0501″, while the best QGIS can do is “NAD83(HARN) / Colorado North”.  When projection information doesn’t agree exactly, I get [...]

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ArcGIS Authorization Error: 7174

When installing an evaluation copy of ArcGIS Desktop 10, you may receive an error message during authorization saying something like “7174: Authorization request for EVA123456 cannot be completed.”  Trial and error suggests that this error is caused by a conflict with a previously authorized installation using a different evaluation code.  Even though you may have [...]

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Iterating in ModelBuilder

One of the most exciting new features in ArcGIS 10 is the introduction of iterating tools in ModelBuilder.  The ability to step through a list has always been a mainstay of programming and computer science, and has been readily accessible to any GIS programmer with a little Python or C# experience.  In previous versions of [...]

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Exporting GeoJSON

If you’ve ever needed to export a shapefile or feature class to a GeoJSON text file, there’s a handy ESRI-supported Python script available.  It’s easy to install into your ArcToolbox, and works quite well: http://arcscripts.esri.com/details.asp?dbid=15545 So what is GeoJSON?  JSON stands for JavaScript Object Notation, an encoding format for web object data.  GeoJSON is just [...]

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Upping the Interval

The hypsometric contour interval on the classic USGS quadrangle maps is 40 feet.  Although it’s not a nice round number, I think it looks fantastic at that scale.  It’s good at representing many different terrain types.  Which is why USGS contours have become a bit of a standard for many GIS and cartographic applications. But [...]

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From CARIS to ArcGIS

If you ever get the opportunity to work with bathymetric data, you may encounter CARIS files.  CARIS is an enterprise GIS suite that is well suited to marine and hydrographic applications.  Many GIS offices don’t have access to CARIS, but that doesn’t mean the data is out of your reach.  CARIS offers a free data [...]

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Revenge of the Map Unit

In my previous post, “When Scale Bars Lie”, I mentioned the dangerous things that can happen when the map unit is not set correctly. As I explained, it can lead to abnormal values, which are often manifested in scale bars.  This week, a friend of mine was using GIS to calculate the areas of some [...]

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