Mapping tips

From Reporting Cookbook: www.forjournalists.com/cookbook

You want to join two tables in ArcMap but can't.

• Make sure the two fields in the tables you want to join are the same the same type. You can't join a text field to a numeric field for example.

You want to change the format of a field in ArcMap.

• You can't change the format within ArcMap, but you can edit the field in another program, such as Microsoft Access, then re-import it into ArcMap.

You want to import a database which includes a ZIP code field in ArcMap but the ZIP code is always formatted as numeric. You want to keep it as text.

• Before importing the database into ArcMap, add a dummy row just below the header row and enter a letter in the ZIP code column. That will fool Arcview into thinking the entire column is text.

You want to organize your data better.

• Use Microsoft Access as a geodatabase and store all of your maps and data in it instead of having them scattered in different places on your hard drive. ESRI has published a book on the subject.

You want to geocode some addresses but you can't afford to buy map data from a vendor and you can't obtain suitable maps from a government agency.

• Use the CENSUS Tiger files as your map source. One tutorial on how to do this can be found on the University of Kansas Web site (PDF).
• Use an online geocoder such as Google Maps or Geocoder.us instead.

You want to analyze crime beyond just plotting the locations of crimes on a map.

• Use CrimeStat, a free crime mapping analysis tool.

You received a CAD file and you want to import it into ArcMap and match it up with your existing maps.

• Instructions on how to do that can be found on ESRI's Web site.

You have an Excel data file with decimal fields, but when you import it into ArcMap as a dbf file, decimals disappear and the numbers are rounded up.

• Follow these instructions from ESRI on how to preserve the decimals.

You want to convert latitudes and longitudes expressed as degrees, minutes and seconds into decimal degrees or vice versa.

• Use an online converter:
  • http://www.terraserver.com/tools/degrees_converter.asp
  • http://www.fcc.gov/mb/audio/bickel/DDDMMSS-decimal.html
• How to do the conversion in Excel

You have a data table with UTM coordinates and you want to convert those to longitude/latitude

• This online converter can be useful.