GIS Tips & Tricks

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

Monday, November 14, 2005

Matching Shade Transparency to Legend

The first time I saw ArcMAP demoed at an ESRI Users Conference in Victoria was many years ago. I remember thinking how cool the polygon shade transparency was and how I thought it would radically change the way I was mapping. Think of it: transparently shaded themed polygons over orthophotography or satellite imagery…How cool is that? Some months later when I finally got to try ArcMAP I think the first thing I did was transparently theme a land-use zones coverage over some orthophoto imagery. Wow, was I impressed! What was less impressive, unfortunately, was that ESRI seemed to go only half way with the transparency feature. Notice how your legend doesn’t change when you change the transparency of your polygons…Strange isn’t it? Maybe we are waiting for ArcGIS 10x?

Of course GIS wouldn’t be nearly as fun as it is without finding a work around solution to little software annoyances.

Here are two quick options to make your legend shade match your transparent polygons?

  1. From the TOOLS menu select the Eye Dropper tool> Customize> Commands> Page Layout> Eye Dropper
  2. Drag the Eye Dropper to an existing ArcMAP toolbar…I usually ‘drop’ it on the Drawing toolbar.
  3. With the Eye Dropper tool selected click on your transparent polygon. The RGB values of the polygon wil appear.
  4. Select OK and the transparent colour is now added to your colour palette.

Option A

  • Switch from the Eye Dropper tool to the Select Elements tool…(the arrow tool) and select the legend.
  • Right click on the legend and select CONVERT TO GRAPHICS.
  • Right click on the legend again and select UNGROUP. Do this twice to make the label patch a selectable graphic.
  • Select the patch box to change and use the Fill Colour tool…(the Paint Can) to pick the colour that was created from Eye Dropper step.

Option B

  • In the Table of Contents select the polygon layer that has had transparency applied to it. Right click the layer and select COPY.
  • Paste the copied layer back in to the Table of Contents but make sure to turn it off so the layer isn’t displayed twice in the data frame.
  • In your legend add the COPIED layer to your LEGEND ITEMS and make sure that the check box for ‘Only display layers that are checked on in your Table of Contents’ is UNSELECTED.
  • Right click the COPIED layer in the Table of Contents again and select PROPERTIES> SYMBOLOGY> match the colours in your copied layer to the colours created with the Eye Dropper tool.

Realistically the above methods are practical if you only have a handful of polygon themes with transparent shades. Also I wouldn’t suggest matching your legend to your transparent shades until you have fully committed to using those colours.

New-School Editing in ArcMAP

I admit that I still edit using old-school ArcEdit, but I'm slowing learning the benefits of the new-school tools as well. For ArcMAP editing neophytes like me, here's a useful link (pdf) to an article describing 11 useful tips and tricks for editing in ArcMAP.

Topics covered include:

  • Modify feature selection by individual layer.
  • Select the desired feature from overlapping selectable layers.
  • Prevent selected features from being moved accidentally.
  • See the feature type or layer currently affected by the active
    snap agent.
  • Control which features snap.
  • Override snapping environment settings.
  • Toggle between the Sketch tool and other editing tools using
    shortcut keys.
  • Use units different than the map units when specifying
    distance for a sketch segment.
  • Cut polygon features based on a specified distance from a line
  • Rotate a selected line feature on one endpoint and snap the
    other endpoint to another feature.
  • Explore a map in detail and perform edits without changing
    the map display scale.

Handclaps to Colin Childs and Keith Mann, ESRI Educational Services for writing this article.

Fixing Broken Data Links in ArcGIS 9

Don’t you hate it when you open an existing MXD file in ArcMAP and those red exclamation marks next to your data layers indicate you have broken data links.

Of course you can always update the data source links individually: Right click on the layer> Properties> Source > Set Data Source…

But if there are a wack of broken data links the above method can be extremely tedious. What if a bunch of GIS data has been moved during some crazy corporate data reorganization? Fortunately, since ArGIS 9, the wise minds at ESRI have made it possible to fully fix broken data links outside ArcMAP in the ArcCatalog environment.

Here’s how:

1) Fire up ArcCatalog
2) Navigate to your .MXD file
3) Right click on the .MXD
4) Select Set Data Sources…

The Set Data Sources window will pop up allowing you to change data sources individually under >New Data Source > Or you can > Select All and change the data sources using a Find and Replace method similar to what you would find in MS Word, Notepad etc… Thank goodness for ArcGIS 9.