Map Editing 151:  Tips, Tricks & Traps

A 20 Minute Mini-seminar for MapInfo Pro Users
Presented at the Puget Sound MapInfo User Group June 4, 1997
John Schlosser, Schlosser Geographic Systems, Inc.

Map Editing Setup

• Make a backup copy of your map layer!

• Display the layer to be edited along with any reference map layers

• Set whether or not to move duplicate nodes in the same map
  Options > Preferences > Map Window [Often you DO want to move them.]

• Set your “Snap” tolerance
  Options > Preferences > Map Window. [Normal tolerance: 5-15 pixels]

• Use a Comment.tab map layer as a scratch pad to note questions/issues.

• Save your tables often!

Map Editing Strategies

• Draw freehand.

• Trace other map lines/regions, using the Snap feature
  Toggle ON=OFF with “S” key

• Make a new region or other shape by combining or splitting other ones
  Object > Combine or Table > Combine Using Column …

• Trim one region with another to make edges match exactly
  Object > Erase…

• Screen digitize using scanned image as backdrop raster map layer.

• Use a digitizing table.

Editing Streets & other Lines

• Display line directional arrows to judge “From” and “To”
  – Map > Layer Control > Display …

• Consider the free LineDirector.MBX It can switch line directions. Download from www.mapinfo.com

• Warning: If you split a street you still need to adjust the street addresses.

• Note: A MapBasic utility could automatically assign address ranges to each piece.

• STRT_ADD.MBX (KGM Utilities) may help if you are adding new streets, not splitting old ones.
  Downloadable from www.mapinfo.com.

• To spot stray, sometimes very short, line segments, display the line objects with a VERY thick line width.

Editing Regions

• Make or re-shape regions from other regions whenever possible.
  Why?  This helps avoid slivers and results in exact registration.

• Make regions with the region tool.
  Why? If you use the polyline tool, you have to take the separate step of converting the polyline to a region.

• Hover along the line [Snap feature ON] to spot “hidden” duplicate or missing vertices.

• Move vertices temporarily to spot double-back errors.
  Use the Reshape tool

• Consider Mapcheck.mbx to look for problems. Download from www.mapinfo.com
  – Warning: Mapcheck.mbx does not spot overlapping separate regions.

• -- To spot overlapping regions in the same or different layers, use a non-solid fill pattern and NO fill [un-check “Background”].
  

Editing Map Data Tables

• Create a thematic map based on the column for which you are entering data. The colors will change in the map as you add or change data values.

• Turn on the dynamic labels, specifying the new data column as the source of the labels.

• Avoid typing text directly into MapInfo where possible.
  E.g., Make a separate (non-map) table with all the data columns filled in, including a unique ID value such as zip code number or Census Tract code. In your map table, only enter the appropriate ID# value. Join the two tables via Query > SQL_Select.

Troubleshooting

• After much editing, you try to File > Save, only to get the message:
  “Unable to save. Out of disk space while editing ...”
  You may not really be out of disk space. Save your work under a new name preferably on a different drive.

• You try to start editing, but can’t and get the message:
  “Cannot perform edit. Someone else is currently editing this table.”
  
  If no one else is editing the table, check for temporary edit files left over from a previous crash or impolite exit from MapInfo. [e.g., files with *.tin or *.tda]