Same same, but different

Interesting comparison of several mapping engines (GoogleMaps, Bing, YahooMaps) and what techniques Google is using to make their maps more readable.

Great data visualizations for number and origin of refugees.

Difficult to grab the impact of the pakistani flood for someone who doesn’t exactly know the size of Pakistan. So, here, a quick composition of Pakistan and its flood, overlaid onto Western Europe.

Nice resumé of current satellites and their characteristics.

Nice visualization of people moving from one place to another.

Nice Web GIS application from the swiss government.

The concept behind BBC Dimensions is relatively simple: take a specific important place, event or ‘thing’, and overlay these artefacts onto a map of one’s local neighborhood.

Great script (in CSS and Javascript) which makes it really easy to display boxplots on a website. Great!

Wonna concatenate numerous fields to obtain all values in a single cell? Here’s the script:

Sub ConcatenateAll()

End Sub

And in order to insert a little bit more complicated string in ArcGIS’s Field Calculator, you need to do this:

"<img src='http://localhost/graph.php?data=36,36,37," & Int([wohnfl_per]) & "' />"

Easy, easy… In Spatial Analyst -> Raster Calculator do:

isnull([My Raster] <= 0, [My Raster])

Just working with some extensive raster data sets. And running into a problem – that is, the values of the raster, although integer, are not being displayed. Here is a solution:

Use the “Build Raster Attribute Table”. And if an error is coming up concerning the reaching of a limit, then use the advanced settings utility has an option to set maximum number of attribute entries.
The utility should be in your install location in the Utilities folder (by default – C:\Program Files\ArcGIS\Utilities). Run the AdvancedArcMapSettings executable and select the Raster tab.

Great visualization of 24 hours of air traffic. Shows well, similar to the Nightlights of the Earth, which regions of the globe are not connected. Impressive!

Attractive and interesting way to sum up the global population.

Gush, sometimes feeling as we’re still living in the 80ies. How do you get data from ArcGIS to GeoServer, classes & colors including?! No easy task. Here is a small lib which makes the export from ArcGIS to SLD possible (with some additional explanations here). Thanks a lot!

Gix, this extension helps GIS developers to migrate ESRI ArcView projects to the most popular Free and Open Source alternatives for Geographic Information Systems (GIS).

Like that one. Lightweight, easy, supply of additional information by mouseover. Really neat.

Nice mapserver, enabling vector display as well. Based on GeoExt.

If you need to calculate the area of a polygon layer in ArcGIS, you can do so in ArcMap.

Use ArcGIS Desktop Help (available from the ArcMap interface) to get basic directions – under the Index, search for “area” – you should then see “Calculating for Polygons”

These directions have been tested and they work well. However, before you do this, there are some things you need to check.

A note about coordinate systems and area calculations
First, make sure that your data layer is in a defined projected coordinate system, like State Plane or UTM. You need to know what the map units of the data layer are (usually feet or meters), because once you calculate area, the area calculation will be in those map units.

If your data is not projected (e.g., it is in a Geographic Coordinate System, meaning decimal degrees) it would be wise to project it first. In the Data Frame Properties, change the coordinate system to a projected coordinate system (e.g., State Plane NAD83 (feet) Texas Central. Then right click on the data layer and choose Export Data. In the dialog box that follows, choose to create the new data set in the Data Frame’s coordiante system (now set to a projected system). This will create a new projected data layer, that you can then add to the Data Frame. From that point, you can follow the directions in ArcGIS Desktop Help for calculating area. If the data frame units were in feet, the area calculation will be square feet.

To convert square feet into square miles or acres or hectares, you need to add a new field to the attribute table (e.g., sq_mile), then use the Calculate Values tool to have that field = the area field x the conversion factor. To get the conversion factor, see Peter Wallin’s the Conversion Table for changing measurement units.

Creating an “area” field in your attribute table if you don’t already have one
If your attribute table does not already have an “area” field, you need to create one before doing the area calculations. You can create the new field in ArcCatalog or ArcMap. Note you can add an acres field using these same directions.

To create a new attribute field for “area” in ArcMap, follow these directions – note you cannot be in an editing session to do this (don’t ask me why):

• Open the layer’s attribute table in ArcMap
• Click on the Options tab
• Choose Add Field
• Name it Area
• For Type, choose Double
• Don’t put anything under Precision or Scale.
• Click OK

Calculating area for polygons (from ArcGIS Desktop Help)

• Open the attribute table of the layer you want to edit.
• Right-click the field heading for area (if there is no field for area values, you can add a new field for area by clicking the Options button and selecting the new field option).
• Click Calculate Values.
• Checkmark the Advanced box (this is important – dont’ forget this!)
• Type the following VBA statement in the first text box (you should be able to copy and paste):
  Dim dblArea as double
  Dim pArea as IArea
  Set pArea = [shape]
  dblArea = pArea.area
• Type the variable dblArea in the second text box (near the bottom of the dialog box) directly under the area field name.
• Click OK.

It seems like 99 percent of the mail we send is electronic these days. The other 1 percent is letters and postcards that we want to postmark with our (usually enviable) location for the recipient. That’s why we dig these uber-accurate Google Maps envelopes.
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