Oct 28 2007

Mile Markers for Arizona Department of Transportation

We have recently begun to work with the ADOT (Arizona Department of Transportation), and were asked to incorporate mile marker data into GPS Insight for them. Of course they have this information somewhere, but in the time that it will take to get the raw data and process it into GPS Insight, we could simply create these mile markers “manually” and I thought this exercise is worth documenting on the blog.

First, I found a high resolution map of the mile markers online via Google.

Then I took a close-up screenshot of the map for the I-10 [I just traveled this last week myself so I thought we could do some interesting analysis of this data later].

Arizona Department of Transportation Mile Markers screenshot

Now I can import this “overlay” into Google Earth and use it as a template for creating the mile markers:Arizona Department of Transportation Mile Markers screenshot 2

Note that the important thing here is that the part you really want to “trace” is accurately stretched over the map — maps and Google Earth inevitably diverge, since maps are never as accurate (or spherical) as Earth. The other roads/borders will not match exactly unless you change the “keystone” using a graphics editor. It would be nice if Google would add keystone as an editable aspect of overlays in the future (keystone is effectively stretching an image more on one side than on the other).

Now that we have this image, we can create landmarks on top of each “10″ mile marker (the map only shows the “tens”).

I-10 mile marker 10 with path

Since this particular mile marker is on the edge of what I considered “accurate” (due to keystone) I measured it myself using the Google Earth Path ruler to 10 miles from the border.

Then a quick copy/paste/rename/replace of the original allows me to quickly place the next 14 “tens” mile markers, placing them on the red dots but on the road itself from Google, which is always far more accurate:

copying Google Earth placemarks

In order to move a copied/pasted landmark, make sure the original is “turned off” (otherwise you can’t “grab” the one you want to rename/remove) and then right-click it, choose properties, and then you can move it when your cursor turns to a pointing finger. Remember to change the name (from 10 to 20, 20 to 30, etc.).

Here is the final product (note I created a folder in “my places” and placed the numerically sequential points along with the overlay map):

final GPS Insight mile markers for ADOT

Then for an additional I-10 definition I will draw a rough polygon landmark around the I-10 which will help me to answer questions like “how much time do my vehicles spend on the I-10 between mile marker 0 (border) and 150 (Phoenix)?”

GPS Insight I-10 polygon border

The key to accurately defining borders around large areas is to use the “compass” area to navigate between clicking between areas. Plus you can right-click to remove your last “incorrect” points and zoom in/out, move, and pan/tilt using the mouse at the top right, since your mouse otherwise is being used to define the polygon.

creating I-10 polygon

Now we can easily find a particular mile marker by typing “ctrl-f” for find, then “I-10 40″ to instantly find/double-click that point for instant navigation:

Instantly find mile marker

And last (most importantly), you can instantly answer questions about your fleet like “How long did Rob (in the Navigator) take driving to, then back from DisneyLand last week on the I-10 in Arizona between mile markers 0 and 150?”

run GPS Insight report

We see it took me 1:50 to get TO Disneyland on the I-10 and 1:41 to get back during that same stretch of road, and that it took roughly 3 days and 7 hours from the time I left Arizona to the time I returned (since it is on the border at Mile “zero”), by running this report (which takes a split second to complete):

GPS Insight polygon report

And here is the actul trip itself along with a 6 minute stop (we were traveling with our kids…):

rest stop

You can see we made it a whopping 83.2 miles before hitting the first of what was many rest stops on our way to DisneyLand…

rest stop

And that stop was apparently at mile marker 87, 3 miles before 90, between the 80 & 90 we just created:

mile marker 87

Thanks for reading through this practical example of how to use GPS Insight and external mapping resources (ADOT mile marker maps, Google Earth, etc.), along with real GPS data to answer questions you may have about your fleet. Of course ADOT would want to answer other questions (response times to accidents in certain areas of the state, proportion of their vehicles in any one particular concentration) but having these landmarks and polygons in the GPS Insight system helps them (and all of our customers) to answer these types of questions.

Here’s the Google Earth file for you to see the results (minus my DisneyLand trip):

http://www.gpsinsight.com/tmp/ADOT Mile Markers.kmz

Rob.

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