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Creating a Trail Profile with Mapping Grade GPS
I am hoping this surveying community can lend technical expertise on this topic.
The web is rife with recreational GPS users mapping trails with watches, smartphones and the like. The MTB community is one of the strongest proponents of creating trail data. USGS absorbs these data and has discussed this as an approach to “map trails”. See https://www.imba.com/news/us-geological-survey-partnering-imba . I humbly disagree. My opinion is to tie any professional GIS representation of trails with mapping grade GPS that ties data to CORS and hence the NSRF in both horizontal and vertical reference frames.
I output positions(GIS call these vertices) along a trail line in Geographic (Lat/Long) and orthometric height. I enter said coordinates into an Excel macro that produces 3D distances between these positions and graph these for publication along with the linework for 2D maps. There is much controversy that we (GIS) should not be doing this. We should be using RTK etc. Yet, I think my mappers, with good skills, excellent hardware can produce the 3D distances over any length of trail that mimics Ground distance over any trail of any length – quickly, efficiently, and with attributes demanded by facility managers. Simple geometry says the hypotenuse between two positions can be calculated to produce slope distances A logging rate commensurate with trail nuances can provide such data that is precise for very large mapping scales.
I’ll share my Excel macro (designed by my Civil Engineer cousin) and the process for Trimble Pathfinder Office workflows for anyone to test. Basically, Lat,Long,Elevation in a CSV is all that is required. Email me at [email][email protected][/email]
Am I committing survey heresy by such an approach? Are you as surveyors being asked to produce “ground” trail distances and have solved this dilemma for the public?
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