TIGER vs. Google Earth: What to do when they disagree?

[treblesum81]

Hi All,

Just like the title says, I'm looking for advice on which data to use when TIGER data, 1:24k Topo maps, and Google Earth imagery all disagree. At this point, they are mismatched about track locations and quantities along a stretch of track between Coolidge, KS and La Junta, CO... Both the TIGER data and the Topo maps show there being several sidings in each of the small towns along the route, whereas the Google Earth imagery show single track in the majority of the same locations, or even nothing at all.

Now, I know that there is the distinct possibility that one (or all) of the data sets is out of date, but I'm not really sure which is going to be the most accurate / appropriate to follow. While I'm somewhat sure that the Google images are newer than the Topo maps, I'm also aware that the images can be up to 10 years out of date in some circumstances (in this area, the photos are dated at 2005), so I'm not sure which I should use for route modeling. Any advice would be appreciated.

Thanks,
Greg

 

[AJ_Fox]

Google Earth shows actual images of the land. Land does not change much. Of course you have to interpret what you see into what you make.

Best of luck for you.

Cheers

AJ

 

[colorado71]

It is maybe because the railway transportations were more important in the past than today. Consequently the railway companies reduced their capacities in many stations. The same situation can be found in many countries from Europe.

 

[Dermmy]

TIGER data is odd. i have no idea how it is compiled, but later dates appear to include additions, but exclude deletions.

Topo maps should be correct for the published date, but free maps tend to be older than maps you pay for.

Google Earth is reasonably up-to-date, most screens show the source and date of the image...

Andy

 

[Jerker]

G'day treblesum81,

I am with Dermmy on this one. I, for one, have never been one to recommend TIGER data (why, if it is 'the bee's knees', does it NOT exist - or embraced by any governments - outside the Continental United States?). The difference between Topographic maps and Google Earth is fairly easily explained - as Dermmy points out - by the fact that Topo maps WILL be correct for their official published date (and as it has been my experience) will tend to publish information that may be considered historical up to that point, whereas Google earth is, because of it's very nature, a 'snapshot' of how things were at the point at which the image was made. You must use all of the information provided from each of these sources, as deemed fit, to determine the final result that you require...

...the important thing is that they do not differ markedly as to the location of any given railway line...

Jerker {}

 

[cascaderailroad]

DEM's and, Hog/Tiger lines are up to +/- 20', or greater, off, in the x-y-z placement. And rivers are sometimes shown way up on hillsides.

Laying Basemaps with GE or Topo maps superimposed, in conjunction with Hog/Tiger lines can help you find proper locations for rivers and RR lines.

 

[treblesum81]

So, really the answer is "it depends"...

TIGER is usually older, but it is quick to work with.

Topo is accurate for its publish date, but that could be many years ago, and sometimes, at least when dealing with the USGS free offerings the map date can change by up to 25 years in the space of one kilometer.

Google is the most up to date, but it can also be old, and is often not high enough resolution to really get a good view of it all.

Really confusing if you ask me, but its what we've got to work with. As far as my original question goes, it seems that the Topo maps, and to a lesser extent, TIGER, offer up the correct(ish) date(s) range(s) for the route I'm trying to build, so I'll stick with them, though Google Earth may come in handy for filing out ground textures and such.

 

[Dermmy]

I use Tiger on the screen with a printout of the best paper map I can find on the desk alongside. Deducing exactly where the Tiger lies should be is easy if there is a river nearby (and fortunately rail lines often use river valleys). The river MUST be in the bottom of the valley, so if the river is 50 meters up the left hand hillside then it is a fair assumption that the rail line is offset by the same amount. This is generally confirmable by a quick check of the paper map. Where there is no river it can be harder, but if there is no river it is probably comparatively flat terrain and the rail line can be off a bit without effecting grades etc.

My route building philosophy though is 'near enough'. I do not set out to produce an exact duplication, just something that gives the feel of the place. If you want exact then consider TransDem and the best on-line or paper maps you can buy....

Andy

 

[RPearson]

Tiger data is digitized off topo maps of the area so won't be more and probably is less accurate than the maps it's taken from. It wasn't designed to be highly accurate - it's published by the US censis bureau.

Bob Pearson

 

[treblesum81]

My route building philosophy though is 'near enough'. I do not set out to produce an exact duplication, just something that gives the feel of the place. If you want exact then consider TransDem and the best on-line or paper maps you can buy....

Andy

I do already have TransDEM, and I've started heavily leaning towards the Topo maps for the rail data and the TIGER maps for things like roads, rivers, power lines, etc. I know they will be off a little, but with baseboard filtering and a little bit of tweaking, they will help me to quickly populate the landscape with towns and geographic features. Another reason I think Topo is my best bet (for rails at least) is the fact that they have most of the old yards and sidings that just don't exist today, and, since I'm going to be focusing my route in the 1930's-50's era (before airplanes and trucks killed off the vast majority of rail usage), having this information is important.

I also think that there is a point where you just have to say its "close enough"... In reality, you could spend the next 10 years working on a route and never get every last detail right, so you really need to focus on whats important and let the rest work itself out...

I think I may still use Google Earth, but only for ground texture matching, as its just not detailed enough to get good imagery, and its the most modern of them all, which means that there will often be buildings and roads where track should be...

 

[R707]

I also think that there is a point where you just have to say its "close enough"... In reality, you could spend the next 10 years working on a route and never get every last detail right, so you really need to focus on whats important and let the rest work itself out......

Hi Greg,

I have been building my route for 10 years, or it just seems that way. Trainz is always a work in progress.

I can see you are a fussy guy, and that is good for the community. You will bring fresh ideas from your experience.

Focusing on what is important!! Well, in Trainz, it is just like model railroading, and the old saying from the model railroader magazine says......model railroading is fun. Still true today.

Please enjoy.

Pete :wave: