SurveyCTO distance calculation guidance
Saahil Karpe 2016-06-17

This Distance Calculator tool is a chunk of code that can be used as part of a larger SurveyCTO instrument that is being used to carry out data collection in a fixed geographic area. Using a central node (village centre, school, a point on a highway etc.), this tool identifies and displays the distance from the current location to the node. It is useful for instances when data collection needs to be carried out within a certain radius. This version of the instrument for example, was used to canvas 800 meters around a number of target schools (in East Africa) and census each household in therein. 

The tool works best when tablets capture the GPS locations accurately and efficiently, but is also designed to work with data collection using a standalone (traditional) GPS unit. Note that in the latter case, the format in which GPS is being collected is important; and by its very nature is more prone to data entry errors. 

Along with the CTO excel sheet, there is also a CSV. This sheet should contain the data points of all the nodes that are to be approached in a given round of data collection. This is especially useful if teams of enumerators are headed to multiple villages/schools simultaneously. 

Steps to use tool: 
1. Before data collection begins, capture the GPS point of the central node.
2. Update the "school_location.csv" document to reflect this GPS information. (Note that if you change the name of this document, to say "village_location.csv", you will need to make sure that this amendment is reflected in cell P10 of the CTO sheet.
3. Your instrument is ready to run. Upload the .xlsx as the instrument and the csv as a supporting file. 

A note on enumerator training: In the current version of the tool, the enumerator is allowed to over-ride the distance calculated if it is obvious to her/him that there is an error. In order to remove this override, remove line 22 and make the necessary change in the relevance in line 23.