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September 27, 2007

Quick Guide to using UTM Coordinates


September 21, 2007

Clipping Raster Layers in ArcMap

Students can use the county land use map.mxd file in the H drive !!!!ACIC folder to create their map. They will need to disable the current clipped county to select their county and may need to manipulate the layout view based on the shape/size of their county.

The Orning Land Use data is available from the ACIC computers on the Mapfiles drive. See MNMapS\Data\LyrFiles and choose landuse.lyr.

ArcMap users may encounter problems when attempting to clip a raster layer to a certain extent. For example, you may be trying to show land use or demographic data for a county. If the data layer covers a wider geographic area, the usual procedure is to use the ArcToolbox "Clip" tool to show only data within a specified area. To do this you would open ArcToolbox and select the "Clip" tool under "Analysis tools" -> "extract". You would then input the features, the clipping pattern, and the output data. Unfortunately, when the data you wish to clip is a raster layer, it will not show up in the Clip tool's available layers.

To get around this problem, it is possible to clip the entire data frame. This will cause only data within a certain region to be displayed.

To clip the data frame, first select the area you want to use as a boundary. If you only want to show data within a county, you would use the Select Features tool (an arrow with a square next to it in the toolbar) to select the county you are interested in. Selected features are outlined in light blue. Next, right-click on the active data frame (a yellow icon usually on the left sided of the ArcMap program, it may be named "Layers"). Select "Properties" from the bottom of the drop-down menu. In the properties dialog, click on the "Data Frame" tab, and check the box marked "Enable" under the Clip to Shape section (about halfway down the window). Next, click the "Specify Shape" button, and select "Outline of Features". If you selected a county, you would choose the appropriate layer for county borders from the Layers drop-down list, and "Selected" from the Features drop-down list. Click OK on the clipping and frame properties windows, and your map should now display only the data inside the selected area.

You can also use this method to clip to shapes or boundaries drawn onto the map. For more details, go to ArcGIS Desktop Help (press the F1 key in ArcMap), and search for "Clipping data frames to a custom shape".

Convert Lat Long to Township and Range


September 20, 2007

Digitizing and Vectorizing Raster Images

'Heads up' digitizing of a raster image allows an individual to make a digital vector copy of a portion of a paper map. This process is manual digitization by tracing a mouse over features displayed on a computer monitor. Documentation of this process is found in the ArcGIS 9.2 Desktop Help under Editing and data compilation, Creating new features. Access the help documentation by pressing F1 in ArcMap.

Vectorization of a raster image allows an individual to make a digital vector copy of an entire paper map. Automatic vectorization is an automated process that converts raster data into vector features for an entire raster or a portion of it based on user-defined settings.This process uses the ArcScan extension, available in the ACIC (ensure the ArcScan extension is activated in ArcMap by clicking the Tools menu, Extensions, click ArcScan and close). Documentation of this process is found in the ArcGIS 9.2 Desktop Help under Extensions, ArcScan. Access the help documentation by pressing F1 in ArcMap.

September 18, 2007

Maps Distortion and Meaning

Maps Distortion and Meaning by Mark Monmonier

Demographic Comparison Tool


September 11, 2007

Measuring Distance

World Mapper - skewed maps based on data - http://www.sasi.group.shef.ac.uk/worldmapper/index.html

How Far is It? http://www.indo.com/distance/

City Distance Tool - http://www.geobytes.com/CityDistanceTool.htm?loadpage

Latitude and Longitude LookUp - http://www.spreadsheetconverter.com/samples/shortest_distance.xls - spreadsheet that calculates distances or http://www.spreadsheetconverter.com/samples/shortest_distance.htm

How Do You Calculate the Distance Between Points? - free tool for ArcMap - http://www.urban-research.info/ur/GIS%20Skill%20Builder-distance1.shtml (Comments at http://groups.google.com/group/comp.soft-sys.gis.esri/browse_thread/thread/a08eda6d062a5109/3ebdd4fd5c629e19)

Great Circle Calculator - http://williams.best.vwh.net/gccalc.htm

ESRI - Measuring distance between points forum discussion - http://forums.esri.com/Thread.asp?c=93&f=995&t=91074#441100

Spider diagrams in ARcView

Script or Hawth's tool possibility - http://forums.esri.com/Thread.asp?c=93&f=982&t=193451#575225

September 5, 2007

Public Land Survey System