As I ‘pen’ my inaugural post, I can already see that I’ve likely spent more time than I care to (and perhaps should have) on this topic I’m venturing into.
It has taken me out on three and a half mile lunch-time jogs, returning perhaps to the olfactory dismay of coworkers. It has brought me out to desolate dark-lit industrial parks in the dead of night to the chagrin of my wife.
Yet such is my nature when I land a new ‘toy’ with functions waiting to be discovered and validated.
Heard of it? Via this app, the Google Latitude service can be used to track the locations of known and consenting cohorts. Hey, accountability is good, right? No more need to call my wife to tell her I’m on my way to pick up our princesses from dance school. And should I get offed from the bike on a canyon run, you know I’ll be praying for good satellite acquisition.
Now as an engineer, I’ve have come to appreciate various things mapping and survey related, not the least of which is the cost of professional equipment and services. And while I have no delusions about matching the precision or even accuracy of data acquired from professional grade GPS units, I have been curious to gauge just how useful data captured via GPS enabled phones can be. To what end can such data be applied? I note at this point that not all phones are created equal, so in actuality, I am focusing on just my particular phone model. To my knowledge, the Apple iPhone and Samsung Galaxy S units are represented in our office. Do I smell a challenge? Keep an eye out for a response.
Back on point, I proceeded to equip myself with a few more tools for my undertaking.
One of these was My Tracks by Google:
This nifty little app allows a user to view their GPS acquired position and view it superimposed upon Google Maps. Information pertaining to lat/long location, elevation, distance, time, and speed are presented in real-time. In addition, the user can record a track, which creates a data log containing the above information, and also set ‘waypoints’ to record a specific instantaneous location. Tracks can be uploaded to a Google My Maps, and an info summary to Google Docs (say if you want to track your running trends for a particular route). Can you say Google gaggle? Furthermore, data files can be exported in CSV, GPX, KML, and TCX formats. I’ll likely present more on these formats in future posts, as functionality dictates.
With the above tool, I set out to acquire the locations of three known horizontal benchmarks I had used for a project I had previously worked on. I already had the ‘professionally’ surveyed points in a Civil 3D drawing, with the point coordinates based upon the California State Planes Zone II – US foot coordinate system. My intent was simply to set my phone atop the exposed brass monuments and record them as waypoints.
Fast forward through the aforementioned excursion under the cover of night, and we have the following data. After creating a point file format to import the waypoints using decimal latitudes and longitudes, I found the horizontal ‘error’ offsets to be 2’+, 5’+, and 15’+. There appeared to be no pattern in the tendency of the errors worthy of mention. Perhaps the small sample set is to blame.
In any case, off the top of my head, it would seem that the use of such data may be sufficient for doing things such as tracking a rough path through unimproved land to lay out a simple agriculture use road or private drive.
Not quite sure yet what to make of elevations as I have to do some homework on it.
Some of my research has also pointed me to the time of day being a factor when acquiring GPS data due to satellite availability.
These and other considerations I hope to look into further and report on in future posts.