I have a csv of a GPS trace with lat-longs that I want to convert into a line so I can measure the distance. My workflow was as follows:

1) Import csv into ArcMap 10.4

2) Convert latlongs to points and create a feature file

3) Use points to line tool in the Data Management toolbox to draw a line from the points (the points are in sequence and have unique IDs)

4) Measure the length of the line feature by calculating geometry.

The csv had 277 points; the calculated length of the line feature after step 4 was ~21 km. However, when I do the same calculation using other software (e.g. using geodist command in stata) or by manually measuring the distance between the points (using the ruler tool in ArcMap), this distance comes out to be ~18 km. I cannot figure out why this discrepancy is occurring. At some places, the points are overlapping (as shown in image below), but I would expect this to results in higher estimation of distance when measuring as distance between points compared to the length of the line, and not a lower one as is currently. Can someone provide insight as to why I am getting this discrepancy? As of now it seems the points measure (18 km) is the correct one and not the 21 km one. Why is the line length feature not showing the right results?

Some overlapping points with line feature cutting through

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  • Remove duplicate points and repeat workflow. Perhaps your line goes backwards. – FelixIP Jul 20 '18 at 22:24
  • Is the line feature class also in lat-lon? – mkennedy Jul 20 '18 at 23:59
  • @FelixIP the points are in sequence and I have looked closely at the points and the line and it does not go backward. Its a trace of a moving vehicle so I don't think that's it. – Ayesha Shahid Jul 21 '18 at 0:54
  • @mkennedy I am not sure what you mean by that question. The line is a feature class with a single row in the attribute table with three columns: "FID", "Shape", "Id". I added a 'length' column. Another point to note is that I projected the line to WGS 84 mercator projection before I could do the calculation of length. – Ayesha Shahid Jul 21 '18 at 0:56
  • It will take less time to test my suggestion, than typing your reply to it. – FelixIP Jul 21 '18 at 1:07

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