Difference between revisions of "Map Index"

A map index is used with a grid to locate features in a map. This will describe a process to generate the index for the street map.

The street map index looks like this:

• ABBOT'S LN: 17K, 17L
• ABBY WAY: 15O
• ACME ST: 15J
• ACORN BEND: 20L, 20M

It's a list of street names followed by a list of the grid cells that contain the street.

First, dissolve on the feature class being indexed. Dissolve is in the toolbox under Data Management Tools > Generalization. Select the centerline layer for Input Features and select FULNAME for the dissolve field. Other settings can be left as defaults.

Next, do a spatial join of the dissolved class to the grid. Spatial join is in the toolbox under Analysis Tools > Overlay. Select the dissolved layer for Target Features, select the grid for Join Features, leave it as a 1-to-1 join. In the field map of join features, right click the field with the grid cell id ("Grid_Num" in this example) and open the properties. For Merge Rule select "Join" and for a delimiter enter ", " You might also need to increase the length of the field to accommodate a long list. If you get an error like "ERROR 001156: Failed on input OID 507, could not write value '13K, 13L, 14L, 14M, 14N, 14O, 14P, 15P, 15Q, 16Q, 16R' to output field Grid_Num" then the field was not long enough. I set it to 1000 so it will succeed and then later I'll manually cull the culprits like "PRIVATE DR" and "PUBLIC ALLEY".

Export the table to a text or dbf file then open it in excel. Get rid of all the columns except street name and the list of grid cells. Add a column and fill it with "=len([address of grid cell list])". Sort descending on this length column and remove the top entries for major roads and the common generic names like "PRIVATE DR". For roads with more than 3 or 4 cells listed, you can edit it down to the start and end cells e.g. "08F to 14F". Consolidate N/S/E/W streets in to a single entry.

Once you've cleaned up the data you can format it for export. In a 4th column enter the formula "=concatenate([street name], ': ', [grid cell list])" then copy the column and "paste special" it as values. The goal of the next step is to get a good balance of number of columns vs column length in order for the index to fill all the available space in the map so the text is as large (thereby readable) as possible. Break the single column up in to side-by-side columns of 100 or so. Once you've done that, copy and paste them in to arcmap then resize. Check whether the resulting table is too narrow or wide, adjust, and repeat. This is a cumbersome process, so edit in a better way if you know one.