HDMapper™ Data Summation Lists
Q: How can I get a list of map objects that are included in my coverage area?
A: For TAP 6.0.2080 and later systems with a Maintenance Subscription date of May 31, 2006 or later, you can use the Data Summation function to create a list of shapefile point objects in your coverage area.
The Data Summation function is used to determine a total of shapefile database values that are included in any polygons on your map. For example, a Population Count (which is a special kind of data summation) allows you to use the rectangles computed for a TAP Tile study (the polygons) and find the sum of all the census population values (the points) that are included in the coverage study.
The Data Summation and Pop Count functions allow you to set the values you want to use. For example, in the Pop Count function, you can select the field strength levels you want to set, and the population points will only be added to the summation if the field strength of the tile that includes that point is within the selected field strength range.
With the added List functionality in the Data Summation function, you have more flexibility. In the earlier version, you could only select numerical database fields. That made sense since only numerical fields could be added to get the total.
With the new feature, you can select text fields as well. If text fields are selected, the content of the database field is written to the data summation text file (along with the totals of any numerical fields you select).
For example, suppose you have a shapefile that includes hospitals in your area, and you are interested in finding which hospitals are included (or not included) in your computed coverage area.
After you have computed the field strength values with HDCoverage and added the hospital shapefile to your map you could view the results:
To use the List function, click the Data Summation button:
The Data Summation form is displayed. Select the polygon layer you want to use for the summation, the coverage layer you created with the HDCoverage study:
Select the database field you want to use. Since we want to use certain field strength levels, DBU_FIELD is selected. This is the name of the database column that contains the field strength values in studies created by HDCoverage.
You can enter the range of values you want to search, or you can double-click the From and To boxes to use the Mobile Facility lookup function to get the Required Field strength values for different mobile configurations and environments (All values in this example are for illustration purposes only. You should determine the appropriate values for your particular application):
For each point-type shapefile layer, you can select the database variables in the layer you want to include:
Remember, if you select a numeric field, the values will be summed together. If you select a text field, the text values will be written to the file
When you are ready to run the function, click the Continue button:
A progress form will be displayed while the database is searched for each shapefile:
A summary form is displayed when the study is complete.
Cascade studies enable you to “daisy-chain” studies, using the results of one summation as the starting point for another. This option is only useful for numerical summations. For creating lists, as in this example, click the No button.
The Notepad file created by the study will be displayed. The file shows the layer(s) used for the search and the range of field strength values included:
The variable and contents for all the points found in the specified coverage area are listed.
Remember, for large shapefiles, this list could include many more entries than in this simple example.
You can also use the function to find a list of all the entries that are not included in your coverage area. Set the “From” and “To” range limits to be below the minimum required field value:
These results show the list in that range (where no adequate coverage is available):
You can zoom into the map and use the Mouse Tips function to identify the points in the “No Service” area that are on the list:
 |
Copyright 2006 by SoftWright LLC