Producing a Large Image from OpenAerialMap

One of the things that users often want to do within MapServer or other tools is to hook up to existing caches of high resolution aerial imagery, like VirtualEarth, Google, etc. to get an aerial basemap that is as high resolution as possible, preferably for free. This applies to cases other than serving web maps as well: for example, the EVS Islands blog has been using Google Earth imagery to derive datasets from for some time now, and is now acting as if there is a product that Digital Globe is selling which could fill this need.

Of course, many users also want a pony.

In some cases, the imagery you see in Google Earth is something you can’t even buy for use online — so with all the money in the world, you might find yourself short a high resolution dataset, or so you might think.

It turns out that for some areas of the world, there is a lot of *public* imagery available. Instead of depending on commercial providers, and the restrictions they entail, you can turn this free datasource into a source for your own maps. OpenAerialMap has begun the task of collecting and collating these images for you, so you don’t have to have your own WMS to see the latest data from the USGS dataset in your maps. (It’s still in its early stages, but it’s getting there.) Now, I understand that in the less enlightened parts of the world, this is not yet the case, but we’re getting there, slowly but surely.

But what happens when you don’t want a map, but instead want an image that you can include in your print-resolution magazine spread?

Open Source Software happens, that’s what.

GDAL has the ability to read images from a remote WMS server, and treat them as it does any other data source: which means that it can take the images, and convert them to any other format, from JPEG2000 to GeoTIFF. And it doesn’t even require any system dependencies for Windows or Linux: Just use Frank Warmerdam’s excellent FWTools. FWTools wraps up all the tools you need to work with geographic formats, be they raster or vector, into one neat package.

  1. Grab FWTools: Linux, Windows
  2. Unpack/extract it.
  3. Run the install script in the root directory.
  4. Grab and save it to the root of your FWTools installation.
  5. Open a command line prompt in the FWTools directory.
  6. Type: bin_safe/gdal_translate -projwin -93.246226 44.892179 -93.195672 44.866816 -outsize 9424 4728 -of JPEG gdal_wms.xml airport.jpg

End result? A 10000 by 5000 mosaic of the Minneapolis-St. Paul International airport, using data loaded from Public Domain USGS aerial imagery — some from Ramsey County, some from the Twin Cities overflight, both higher than 1M resolution (.15 and .3 respectively) within the past year and a half — and the speed to create it is essentially as fast as your connection to the net.

You can try this at home, and once you have the image, you can do *whatever you want with it*: The data involved is all public domain, and there is nothing to stop you from doing anything with the data. You can convert it to another format, derive vectors from it, print it out on a giant poster board, etc. No attribution or other sourcing necessary, because the data is public.

OpenAerialMap is all about the sharing of data that you should be able to get access to anyway, and as you can see here, in some cases the data that you wish you had you have access to already — you just didn’t know it yet.

14 Responses to “Producing a Large Image from OpenAerialMap”

  1. Mr Minton Says:

    First – DigitalGlobe does NOT have a D(igital)G(lobal)I(mage)M(osaid) product. This product idea is mine alone. I am determining if there is a market and, if so, would DG allow their data to be used toward DGIM’s development.

    Second – DigitalGlobe makes lots of bucks off of it’s primary hi-res imagery products. They have a sufficent number of “deep pocket” government and business customers to sustain and grow their current business. The DGIM product of islands is aimed at an untapped market that has needs for hi-res imagery, but no “deep pocket” to purchase from. My proposed price points, $25 to $150, are in line with DG’s own Image Atlas product line.

    Third – If the DGIM product of islands has the market I suspect, if DG approves the use of their imagery, if the price point can remain attractive – then I would be glad to ride this “pony” just as far as it will take me.

  2. John Cowan Says:

    “It doesn’t even require installing any software” — just install the following software. Umm?

  3. crschmidt Says:

    John: It doesn’t require installing any software systemwide, which is the part that typically bothers me. You’re right that the wording of the post is totally unclear: the key thing about FWTools is that it’s a ‘self-contained’ package. I don’t really know a better way to put it: I’ll remove that bit instead. (It matters to me, but likely not to anyone else.)

  4. crschmidt Says:

    Mr. Minton:

    Read your most recent blog entry. No other ones — just that one. Especially the sentence at the very end: “Now, the DGIM product at $25 to $150 is an affordable option. No shipping and handling, just digital downloads.”

    Try and tell me that without context that doesn’t indicate that there’s a product available: not only that, but since you’re displaying the imagery on the web, I believe you’re also hocking a product that *can’t* exist, since Digital Globe has exclusively contracted their high res stuff for web display to Google.

    In any case, whether you can get what you want for $25, $50, or not for any price due to contract restrictions — for at least some cases, you don’t have to spend anything to get data you might be interested in. That’s really the point: The DGIM ‘product’ that you’re touting, whether it exists now or never, is something that people want, and they can, for some types of data, get it for free.

  5. Mr Minton Says:

    Alright, I screwed up with that sentence. No product yet. And you are correct – what I tout can be compiled by anyone with a Google Earth account and the right collection of freeware. Yes, they can, but most won’t. Most of us would rather pay a fair price for something that ultimately costs us our most valuable asset – time.

  6. crschmidt Says:

    Mr. Minton:

    I think you’re perhaps missing the point: the images that you’re ‘offering’, or that you put together, are not “yours”. You don’t have the rights to sell them, and in fact, you may not even have the rights to derive the data you are deriving from the imagery. If you don’t understand this, reading through the links and comments on James’s post from a couple months ago may be informative. One comment which I personally agree with, and is worth taking into account:

    “There are situations where a GE screenshot could fall under fair use (scholarship and review, etc), but I highly doubt that any of those situations would also involve a real GIS app.”

    Using the data the way you are right now — displaying it on the web — may be fair use. But the 7.7MB “DGIM” you posted is almost definitely a violation of the Terms of Service for GEarth, and using or distributing the image is almost definitely a violation of the copyright of the image.

    Maybe that doesn’t matter to you. I don’t really know what your goal is in posting it. However, if it were me, compiling a bunch of screenshots from Google Earth, posting it as a file for others to use would be something I would personally avoid, much less participate in any activity that I might think of being commercial with.

  7. Darren Cope Says:


    Great post as always! I was just thinking of this on Friday, as I need some imagery in .tiff format, and figured OAM and GDAL would come to the rescue. However, I didn’t have time to investigate–and now I see you’ve posted step by step instructions before I have to figure it out myself! Fantastic! I’ll be giving this a try soon!

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  9. Randy Horner Says:

    Minton seems to be someone who loves islands and GIS. I’ve enjoyed his information for some time and I can’t image he has anything but good intentions. No doubt you are correct in your assesment of legatiliy of the situation but comments like “Maybe that doesn’t matter to you” seems a little harsh. Of course, maybe that doesn’t matter to you.

    Love your blog.

  10. Daniel Says:

    In regards to Mr. Minton’s post — he actually falls within the appropriate crediting guidelines as he points-out the source to the imagery in the context of his presentation about that source product. He is proposing an idea, and nothing more.

    To note, it is considered good form to include a credit to the imagery source even if that source happens to be public domain. There are other reasons for doing this — generally toward the need to fulfill the information gap of tracability back to a source, and so that accuracy can be documented.

    This would also generally depend on its end-use — or to what extent you might have modified the source. (If you made the source more accurate, for example — then why would one wish to establish information that might create the misconception that the new product is less-accurate due to its initial source being less accurate.)

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  12. PerryGeo » Impervious surface deliniation with GRASS Says:

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  13. Simone Bonzano Says:

    I’m interested to grab aerial maps for my area of study in the Eastern Anatolia (Turkey), can you give me some hints to change the script to do that? I’ve tried changing only the coordinates but it doesn’t work.

    Thank You

  14. Dave X Says:

    OpenArialMap has not been serving imagery since 2008-12. says:

    “ is currently offline and no longer serving imagery tiles. “