GIS Tips & Tricks

A weblog dedictated to the lifelong pursuit of cartographic bliss in GIS.

Thursday, February 23, 2006

Overlapping Polygons Display Order

Recently someone asked me how to change the display order of overlapping polygons (like region topology) from an SDE layer in ArcMap. The problem was a smaller polygon underneath a larger one was not shown when the unique values of the dataset were symbolized using a solid fill. Like this:



The solution isn't as intuitive as it could be. For ArcGIS, ArcMAP 9x the display order of the polygons can be changed in > LAYER PROPERTIES> SYMBOLOGY> ADVANCED> SYMBOL LEVELS...>


Check the box next to >Draw this layer using symbol levels specified below and use the up and down arrows on the right to toggle the display order of your polygons layer values.



The polygons are displayed in the order selected in the symbol levels window. See...


For users of ArcGIS 8x the location
of the ADVANCED>SYMBOL LEVELS
menu is a little hidden and is found by
right clicking LAYERS in the
Table of Contents.

Wednesday, February 01, 2006

Cool Tools continued…

An anonymous comment on my previous post suggested that I should check out the free ArcGIS extensions from Ianko’s GIS page. The company is now called ET Spatial Techniques and I have actually used their free Easy Calculate tool which is an excellent add-on for ArcGIS ArcView users. From the http://www.ian-ko.com/ website:

EasyCalculate is a set of expressions (currently 110) for the ArcGIS field calculator. The expressions can be loaded in the Field Calculator and when executed calculate some spatial characteristics of the features, edit the shapes, add records to a target layer, draw graphics etc

I haven’t tried Ianko’s other tools yet like ET GeoTools, ET GeoWizards, and EditTools and the other free stuff like the Watershed delineator but it looks like the focus is primarily on enhanced editing and manipulation capabilities as well as surface generation tools for ArcGIS ArcView users. The tools are all available for free demo and the cost to buy seems reasonable at $110 US for EditTools, $140 for ET GeoTools and $180 US ET GeoWizards. As is the case with most software the price goes down with the number of licenses purchased.

One of the things I have found most difficult about the transition from the command line ArcInfo world to ArcGIS is the editing capabilities in ArcMap versus ArcEdit...anything that can make editing in ArcMap more intuitive and easier is definitely worth a try. The next time I have to do some editing I will definitely take a look at Ianko’s GIS page.

Thanks for the tip “Anonymous”…Keep them coming!