Google Maps and Elevation

Question for you guys....

I'm using [www.geocontext.org] to plot out elevation for a real track.

How accurate do you find this to be in comparison to the real thing? Do you use onboard shots as well to adjust the elevation as needs be? Just interested to know the techniques that others use when it comes to elevation and real circuits.

Thanks.

Google Maps/Earth takes its elevations from a number of sources. In most areas, especially non-urban ones, data comes from SRTM 90m-DEM. It's a good starting point, regarding relative elevations, that is: "this section is in higher altitude than this other section" or "the elevation difference from this point to this point is about 20 meters". And that's really all the useful data you can get from it, it's not that accurate when you consider a single track.

Some areas have better resolution and quality, mostly in the U.S. or important urban centers. For example, profiling Laguna Seca will give you reasonably accurate data. Finally, Google Earth has a feature called "3D Imagery" (don't know if Maps has it too) that is very accurate, even identifying individual trees, but if I remember correctly it can't be profiled, at least from inside Google Earth.

In short, Google data is good as a starting point. To get good results, you need other sources: if you happen to find official construction plans with elevation data, those are probably good enough. Photos and videos (onboard and TV broadcasts) are probably your most important sources. To me personally, it's much easier to "understand" elevation from videos because the movement allows us to see things in 3D in our flat 2D screens.

Long story short: if you're not sure, trust your eyes.


My unfinished tracks: [www.grandprixgames.org]
Send bug reports and track editing questions to f1virtualblog@gmail.com

As Prblanco just said, it's a very good tool to give you the initials, like the total altitude difference between the highest and the lowest point of a given gradient - although be careful, sometimes even that's not accurate at all. But mostly it is. It really is the development of the last year or two - earlier, I found most of the Google Maps/Earth elevation data to be useless.

Onboard shots, I also take with a pinch of salt - my most preferred technique is to get a high quality race video full of outside TV cam shots and just visualise the reference points, e. g. in this section the fence moves out of sight at this point, the track falls away at that point, etc.

Otherwise, I can only echo Prblanco, he really highlighted the most important points pretty well.

Note that elevation building is the single most difficult part of track-making when it comes to accurately modeling real world circuits. Judging angles comes close.

Speaking of angles, you sometimes have to take into consideration how the camber will affect the given part of the curve you are adjusting, it might have a major effect. This goes for bank angles as well, if you are adjusting them later. Setting angles is also especially hard, because there's even less data available for them. Only sporadic - e. g. I've read somewhere that the Shell Oils hairpin at Oulton Park is banked at 10 or 12 degrees and it come in handy. The only track with full camber data is the Glen, which provides info on its official site.

EDIT: As for elevation, before you start, dig really deep into the depths of the internet to get an elevation profile - and I mean, REALLY deep. The time you invest in this will come in handy later on, when you do the hard work of editing. E. g. I've found a profile which proved to be spot on for the VIR on a scanned page of a car magazine... Or an old photo of the Brands Hatch Indy circuit profile on the 10th page of a Google Images search.

Good luck.

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My workthread - [www.grandprixgames.org]
Full of classic F1/non-F1 track layouts

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Edited 1 time(s). Last edit at 06/07/2015 10:26PM by Atticus..

One more tip: try to get turn-by-turn or corner-by-corner track guides from the web.

Professional drivers and driving school materials very often point out the little undulations and camber of any given corner precisely. Accounting for these in the DAT file, you can kind of micromanage the elevations to the smallest level. The guides also often provide the ideal turn-in, apex and track-out points for vehicles as well, which comes handy in CC-line editing (although be aware that single-seaters sometimes necessitate different lines).

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My workthread - [www.grandprixgames.org]
Full of classic F1/non-F1 track layouts

My blog about F1 performance analysis - [thef1formbook.wordpress.com]

Interesting responses, thanks both.

Finding detailed elevation profiles may be difficult given that the circuit that I'm doing is a street circuit. I have, however, got a copy of every session for that circuit (it's only been used once so far, to my knowledge) so will use that as a guide.

I think what I'll do is use Google Maps as a base and then use the onboards and TV copies to adjust as necessary.

Sounds good.

You are rather lucky that it's a street track as far as the DAT is concerned, because a) they usually have less elevation changes than permanent courses, and b) there are so many things in the TV cam shots to use as a benchmark. (That's before the 3D object builders come in and freak out due to the enormous amount of objects to create, lol. )

Be sure to ask away, if you get stuck or something. Have fun.

---

My workthread - [www.grandprixgames.org]
Full of classic F1/non-F1 track layouts

My blog about F1 performance analysis - [thef1formbook.wordpress.com]

I'm going to let the cat out the bag for the purposes of this thread - the track that I'm working on is from the Putrajaya ePrix, which means nothing, unless you've been watching Formula E.

I plotted the various points a month or so ago using [www.geocontext.org] as mentioned above.

The lowest point is 26.2 meters above sea level, and the highest point is 38.2 meters above sea level, according to Google Maps data. So that's a difference of about 12 meters. I thought that was a lot, but looking at the original F1 2001 tracks on Grand Prix 4, it is on the lower side of the spectrum.

The original Hockenheim, Melbourne, Montreal and Indianapolis have a lower elevation whilst it is about equal to Monza. However...



For a track of 530 sectors, there is a lot of noise present, and quite a lot of elevation that doesn't appear to actually exist, or has been exaggerated a fair bit.

Quote
neldav03
For a track of 530 sectors, there is a lot of noise present, and quite a lot of elevation that doesn't appear to actually exist, or has been exaggerated a fair bit.

Yes, that's exactly what you should expect from Google elevations. As you get more familiar with the track you will know where to trust Google and where to discard it. I see that Street View is available in the region, so it's another reference you can use.


My unfinished tracks: [www.grandprixgames.org]
Send bug reports and track editing questions to f1virtualblog@gmail.com

Thanks for the reply Prblanco.

As it turns out, a lot of the flat areas around the Putrajaya circuit actually look 'flat' with zero elevation (there may be some here and there, but I'll need to go onto the on-board footage to have a look, certainly not as much as the elevation above claims).

However, Google Maps was a very good baseline for around half of the circuit, meaning the elevation now looks like