Measure feature by tracing

Question

I'm trying to measure how far along a river polyline a feature is using the measurement tool in ArcGIS. Is it possible to trace the polyline (in a similar method to the trace tool in an edit session) to get the total actual distance rather than straight line /estimated distance?

(I'm aware that you can have segments with the measurement tool, but over large distances this quickly becomes inaccurate compared to the feature length)

Currently my work around is to create a copy of layer, edit the layer, split the line and re-calculate the length which seems excessive for a quick query for a colleague.

Answer 1

Just in case, you can use Snapping for snapping to the vertices/edges when using the Measure tool. This would not be very helpful though if you have long features with high density of vertices. You would still need to click through the feature, but at least your clicks will be snapped to the vertices or edges (which will increase the accuracy of measurements to some extent).

In case you need to perform multiple measurements, consider using Linear Referencing, see a good post here.

There is an idea on ArcGIS Ideas for introducing this functionality.

You could also write a simple Python add-in that would take two input points and perform the process you are doing manually now and open the message box with the calculated length.

Answer 2

Not that different from your work-around, but what I do for things like that, is I have actually set up a "TEMP_LINE" FC in my SDE and we use for tasks like that so we don't have to create a copy of anything and such as that. I just add a feature to the TEMP_LINE FC using the trace tool. Because it's in an SDE it auto calculates the feature length. Additionally, if you need to change units, you can always do that in the field properties using the already provided shape_length field. You just open up the layer properties, go to the fields tab, select the field, and click on the number format (on the right side) and edit this using the "Rate" option. Using that method, you can have the FC in a projection that uses, meters let's say, and have it auto display the length in feet for you so you don't even have to manually convert it.

Ok, so, I know that's still more work that it seems like it should be because the measure tool should be able to use trace feature, I completely agree. But, that's the easiest work-around I've found. At the end of the edit session, I can even just open up that table and delete the temp line features, or, I have added a "project" and "label" field to that, and I can also save those measurement lines that way and use them for display in presentations, maps, etc... as needed (I just use a definition query on the project field to get the ones I want).

Hope it helps and makes sense, if not, let me know and I'll try and clarify what I mean.

Answer 3

A quick way to measure would be to use the "Measure A Feature" part of the measure tool. Enable the larger "+" button to the left of the measure area button, then click on the feature. - this is also useful for checking polygon areas.

Remember - This will measure the whole line feature. If what you are trying to measure is longer, or made up of multiple features, it might be more convenient to edit and merge them together, or use the dissolve tool, if the attributes are properly set up for that function.

cheers and hope this helps.

Answer 4

If you need to measure a specified length

• make a new line feature and use the 'limit trace length' by editing your new line,
• turn on snapping,
• click your starting point on what your tracing,
• click the trace button on the edit tool bar,
• left click in map and open trace options, -check limit to length and enter the length you need (should default to projection unit, feet, meters, miles whatever it is),
• then trace what your measuring and it will stop at the length you put in.