Leveraging Geospatial Knowledge to solve Geographic Secrets

This post on leveraging geospatial knowledge to solve geographic secrets comes from one of our interped GIS techs, Dan Koopman.


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Urban Exploration is a hobby that has skyrocketed in popularity over the past 20 years in the United States. It is loosely defined as the discovery, infiltration, and exploration of areas traditionally deemed "off limits."

It is probably no mistake that the increase in popularity of Urban Exploration parallels the public's access to new and ever-improving geospatial data in the form of free services such as Google Maps. What started as a technical tool aimed at getting people from Point A to Point B, has raised awareness within the public of what comes between - in other words, the value of public geospatial data beyond driving directions. The discovery and exploration of abandoned places is, at its heart, a geospatial question that begs to be answered and addressed by datasets ranging from high-resolution imagery to census information.

These leaps in awareness and usership, however, have come at a price to Urban Exploration. Increased access to information about delicate abandoned buildings and the resulting traffic in and out has led to many negative consequences in the hobby. These consequences range from increases in security aimed at keeping explorers out of sites, to outright abuse and degradation of sacred historic buildings by vandals.  To counteract this abuse, two unspoken rules obeyed by the community for sites not yet heavily trafficked have been established:
a) The exact location of the site must never be revealed
b) However, Clues leading serious and respectful explorers to the site can be given upon request, so long as some amount of work must be undertaken in order to find the site.

This being said, I hope that whoever chooses to read this article takes from it not a free shot at a really cool place, but an example of how using geographic knowledge in conjunction with free geospatial technology can help you find a virtual needle in a haystack. I also feel comfortable in sharing this since the location discussed is so remote that the effort it would take to reach would not be worthwhile for your average vandal.

Jake Reinig is a talented young photographer and explorer from San Diego, California. I was visiting his website when I came across some beautiful pictures of some double-decker passenger train cars left abandoned in a desert. Reinig, being a responsible explorer, spared only two descriptions in his explanation of the site: in the "Desert east of San Diego." I became so interested in the idea of several large passenger train cars being stranded in the middle of the desert that I decided to try and find them using Google Earth.

I encourage the reader to check out Jake's post that contains the images used to find the trains.

In an initially naïve move, I figured that I could just "fly around" in Google Earth in the desert east of San Diego, and find the cars in the imagery. I soon realized however that this was a ridiculous and ineffective method.

In the last of the pictures on Reinig's post, there is a very distinct conical mountain in the background behind the railroad tracks. I opened up the Google Earth preferences and set the vertical exaggeration to 2/3 - this allowed me to try and match the feature that I was seeing with the digital elevation model that is loaded in Google Earth. Unfortunately, as I found out, there are many conical mountains in the desert east of San Diego. It only took about an hour of fruitless navigation to figure that out...

After the realization that trying to find a train car in 2500 mi2 of desert was literally like trying to find a needle in a haystack, I started to assemble more contextual clues and leverage geospatial information.

I started working under these assumptions:

Specified in Description
* Desert
* East of San Diego
Implied
* It's a railroad
Visually Interpreted Clues
* The trains are on a spur
* The spur likely ends after the train cars
* There is a smallish trestle over a river

It occurred to me that there may not be too many railroad lines running through the desert in that part of the world, so I googled "California Railroads." I cherry picked a very simple map of the all historical railroads in California courtesy of www.djcooley.com and zoomed in on Southern California:



The map reveals that there is only one railroad line that connects San Diego to the desert, and it cuts across the mountains east of San Diego and across the southern part of the Anza-Borrego Desert eastward to El Centro.  I went on the assumption that the trains had to be located on a spur off of this railroad line, narrowing down the potential targets.

At that point, I began to interpret the pictures on Reinig's site a little more thoroughly.
Perhaps the single most important photograph to solving the secret is the second to last one, for two reasons:
a) It shows the fact that the trains are on a spur
b) More importantly, it reveals that the "main line" of tracks runs in a SE to NW fashion. I arrived at this crucial relationship when I noticed that the sun in that photograph is setting. Because the sun always sets in the West, and the main line is closer in the left of the frame than the right, it must have been constructed on a SE to NW trajectory.

Drawing this relationship out on paper gave me a map to compare with the imagery for the area, greatly improving the likelihood of finding the trains. But that's not all - the first picture clearly shows the spur ending after the trains. It also shows a bit of topography to the East of the trains as well as to the North.

Another crucial piece of evidence is revealed in the final picture, which shows the conical mountain. Because of the newfound contextual knowledge that the railroad tracks run SE to NW, it can be assumed that there is a considerably unique conical mountain to the South and East of the trains.

I added these new geographic clues to my list:

Geographic Clues
* Because the sun sets in the West, and this is clearly a sunset, the main rail line must run from the SE to the NW, with the spur roughly N/NE
* There is a very distinct conical mountain to the South of the Spur
* There is a small railroad trestle going over a stream
* One of the photos reveals that there is a hill to the SE of the trains as the photo is looking down on the trains
* There is a distinctive conical mountain to the SE of the site

I also began to look at Geologic clues. In the second-to-last picture, there is considerable vegetation - sagebrush and low-lying desert bushes. The density of cover is relatively high. The first picture shows there to be large sandstone outcroppings and boulders, uncharacteristic of a low desert. I also added these clues to my list:

Geologic Clues
* There are large smoothed sandstone outcrops in close proximity to the trains
* There is sand that has been blown over the tracks
* There is considerable vegetation and brush
* The end of the spur has a large rock outcrop

These new clues brought me back to El Centro. I suspect that it is called El Centro for a reason... To the east there is nothing but sandy flat areas without any distinct topography... This description definitely does not fit in with the land cover seen in the pictures, and is missing that crucial conical mountain feature to the southeast of the trains.

With these clues compiled, a significantly reduced search area began to take shape:

a) EAST of San Diego, in (or near) the desert
b) WEST of El Centro
c) NORTH of the Mexican Border (it's assumed to be in the United States)
d) SOUTH OF or DIRECTLY ON the only railroad that connects San Diego to El Centro.

This graphic shows the only possible places the site could be. The red line represents the railroad line drawn in from the California Railroads Map. The black box shows the West, South and East borders.


I also drew out the trajectory of the main line and spur that I figured out from the sunset picture:

Armed with the Hand Drawn Map showing the clues, I began following the railroad line west out of El Centro. The drawn map was invaluable as you could eliminate any section that didn't fit the 2 dimensional vectors of the SE-NW line. That is to say, there are an awful lot of sections that don't meet those criteria. Still, I was hung up on the location being on the Eastern edge of the mountain range...

I had isolated an area that met the description well - the tracks were SE-NW, there was a conical mountain in the SE, there was sand over the tracks, a small trestle over a stream and even an abandoned water tank - unfortunately there was no spur. I turned on the "Historical Imagery" toolbar and turned on previously acquired imagery but there was no evidence of a spur.

After that failure, I turned on the "Photos" layer in Google Earth and was surprised by how many images came up. Basically, users upload and "tag" the locations of their pictures to Google Earth's servers. These images are then added to a central database and made available through the "Photos" layer.  In the area that I was focusing on, I found one tagged as "Carrizo Gorge Railway."

Without divulging any more information, within several minutes I was tracking the railroad line further west, hand drawn map in hand. When I finally found the site, I must admit that it was not as far from civilization as I had expected. It is actually the quiet neighbor to an, er, interesting type of ranch...

Also unexpected was the degree to which my hand drawn map matched the geometry of the railroad spur when I held it up to my computer screen - it was uncanny how accurate it was.

It only took three hours of intensive research, but through some historical mapping, geologic identification, geographic knowledge, and contextual interpretation it was possible to gather enough clues to resolve a train in the middle of a large desert. Of course, none of the individual parts can lead you there alone; it takes a common platform to make sense of all the data. In this case, all that it took was leveraging a free geospatial platform to find five train cars in a roughly 2500 mi2 area - a pretty decent feat considering that GIS was just a twinkle in someone's eye when the cars were placed there.