OpenStreetMap

DigitalGlobe Satellite Imagery Launch for OpenStreetMap

Posted by @kevin_bullock on 9 May 2017 in English (English)

Over the past few years, as I've attended State of the Map conferences, I'm consistently asked about satellite imagery: how it's processed, accuracy, coverage, availability, resolution etc. I appreciate the fact that OpenStreetMap contributors are curious experts when it comes to satellite and aerial imagery. The reoccurring theme is: accurate, high-resolution and up-to-date satellite imagery is an essential component for improving this continuously evolving map of our planet – whether it’s to trace new features or to use as a reference layer for validation.   Over the past few months, we have been working with several of our partners that share the common goal of improving OpenStreetMap. To that end, they have generously funded the launch of a global imagery service powered by DigitalGlobe Maps API. This will open more data and more imagery to help aid OSM editing for OSM contributors. OSM contributors will see a new imagery source in addition to imagery being provided by our partners Bing and Mapbox. You will now see the following two image services from DigitalGlobe:

DigitalGlobe-Premium is a mosaic composed of DigitalGlobe basemap with select regions filled with +Vivid or custom area of interest imagery, 50cm resolution or better, and refreshed more frequently with ongoing updates

DigitalGlobe-Standard is a curated set of imagery covering 86% of the earth's landmass, with 30-60cm or resolution where available, backfilled by Landsat. Average age is 2.31 years, with some areas updated 2x year.

We anticipate there will be questions and feedback and want to make sure they are being addressed. We already have an active forum with FAQs here https://mapsapidocs.digitalglobe.com/discuss. This post is replicated on OSM Forum and I’m available on OSM help or you can hit me up directly with any additional questions. We are working to provide metadata (image acquisition date) for all of the imagery provided. This will be a huge tool for OSM mappers. We are also going to post the imagery specification.

We appreciate the OSM community’s awareness and diligence for licensing, so we wanted to be clear on the intended uses for this service. We have a short human readable EULA to summarize terms for editing OpenStreetMap :

DigitalGlobe Satellite EULA: DigitalGlobe, Inc. is pleased to provide its high resolution satellite imagery to OpenStreetMap in support of its mapping initiatives. By using our imagery in the OSM editor, you understand and agree that you may only use our imagery to trace, and validate edits that must be contributed back to OSM. You cannot download our imagery or use our imagery for any other purpose. We retain all right, title and interest in and to our imagery. We provide our imagery “as is,” with all faults and as available; we disclaim all warranties, express or implied, to the extent permitted by applicable law. You can recover from us only direct damages up to an amount equal to the fees you have paid to us to use our imagery on OSM, if any. We are not liable for any other damages, including consequential, lost profits, special, indirect, incidental or punitive damages. Happy mapping!

Attribution should be source=DigitalGlobe

DG Blog post: http://blog.digitalglobe.com/news/digitalglobe-satellite-imagery-launch-for-openstreetmap/

Sincerely, Kevin Bullock

Location: West 120th Avenue, Westminster, Adams County, Colorado, 80233, United States of America

Comment from imagico on 9 May 2017 at 17:09

This is great news, thanks to DG and supporters for making this possible.

A quick look at the imagery indicates there is quite a lot of useful stuff in there - even if there is obviously a lot of overlap with imagery we already know from Bing and Mapbox there are also images were existing sources provide nothing of comparable resolution and furthermore there are many areas where having an additional, different image is useful for verification.

Two quick observations from looking over the new layers at a few places:

  • There seem to be quite severe alignment differences between the two layers and DG images from Bing and Mapbox, sometimes even with clearly the same image as basis but apparently processed differently, occasionally several hundred meters in magnitude - like for example in some parts of Norway.
  • The starting zoom level for the tiles with the images is fairly late (z13), especially for high latitudes. This makes using the images for finding gaps in mapping like looking for missing islands, lakes etc. quite difficult since you have to zoom in to get the image but then cannot see a larger area any more. So as a suggestion - if you could extend the tiles by a few zoom levels downwards that would be very useful. The imagery from Mapbox you have for z<13 and the Landsat Geocover fallback imagery is not really of use for mapping, it could even be preferable not to deliver tiles without DG images so the editor shows the image layer below instead.
  • There is currently no recording date metadata available - this would be extremely helpful for mapping. Bing has this and we have been bugging Mapbox to add it for years with no success.
  • Having coverage polygons indicating the image coverage would be great for image source selection as well of course.
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Comment from @kevin_bullock on 9 May 2017 at 17:21

thank you imagico for the feedback!

imagery offsets: I'd expect to see a few meter offset (generally 5m or less). This is due to different techniques in orthorectification. Several hundred meters is not expected. Please send me the coordinates and we can look into it.

zoom levels: understood and thank you. So you would like the high resolution imagery to be viewable in zooms 13, 12, 11 (or something like that)?

metadata: as mentioned in the post, we will be providing it and are committed to that. We will make it available in the coming weeks. This will show both coverage and acquisition dates! I agree this will be huge for mapping.

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Comment from imagico on 9 May 2017 at 18:10

zoom levels: Yes, ideally all levels of course but practically adding z12 and z11 would already be good.

imagery offsets:

Most extreme case i remember was in the Lyngen Alps - around here: http://www.openstreetmap.org/#map=11/69.8068/20.1802

Differences with the same image source can be found here: http://www.openstreetmap.org/#map=13/62.5597/8.1576

Here i get ~50m difference even at sea level: http://www.openstreetmap.org/#map=13/70.1720/22.2797

I know these are pretty nasty areas due to steep relief but i generally would expect at least no larger differences with the same image basis (i.e. the same viewing direction) unless you changed the relief data basis. Offset at sea level to me also indicates insufficient quality relief data.

metadata:

Sorry i read over that part. Looking forward to it.

By the way i forgot to mention: Good to see you were able to keep the terms of use fairly plain and simple so you can actually read them without getting a headache.

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Comment from @kevin_bullock on 9 May 2017 at 18:33

Thanks for the links to the offsets. In areas of high relief, we would expect offsets due to the "look angle" of the satellite and the "lean" of the mountain. As for the sea level offset, we'll look into this. We typically use SRTM as the terrain model which only extends to +60degrees in the North. This is likely one of the contributing factors. Thanks again for the great feedback especially on the TOU!

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Comment from Dalkvist on 9 May 2017 at 19:15

First thanks for making this available!

Regarding only using the SRTM data, there is a 50m resolution dem available for Sweden under ccby4 (the "GSD-Höjddata, grid 50+" data set) if that is of any use. I believe there are something similar available for Norway.

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Comment from NunoCaldeira on 9 May 2017 at 23:33

great. looking forward! keep up the good job

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Comment from Zverik on 10 May 2017 at 09:18

Hi Kevin, and thanks for these layers. They would surely boost the tracing activity in many areas.

Is it possible to add at least one "overzoom" level? That is, where imagery is only up to z17, add a z18 level with scaled-up tiles, using the source hi-quality imagery. That would make for easier tracing, since at the current quality most small features are too pixelated and suffer from jpeg encoding artifacts.

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Comment from JimmyRocks on 10 May 2017 at 12:06

Thanks for all the great work you're putting into this project! I am excited to use the new imagery for our marathons and import tasks! Keep it up!

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Comment from @kevin_bullock on 10 May 2017 at 17:25

Is it possible to add at least one "overzoom" level?

Hi Zverik - where we have imagery available, it should all overzoom or oversample to maximum zoom. I'm trying this right now over an area in the USA and seeing it oversample to z26. My guess is you found an area where we haven't published imagery. We will have coverage and metadata soon, and in the Premium layer, we will have full global coverage in future updates.

Nuno and Jimmy - thanks for the feedback!

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Comment from sommerluk on 10 May 2017 at 17:37

Thanks a lot! That’s great news!

There are many places in West Africa where your imagery is much better the what we had before. I love to see this, espacially because these countries are often forgetten because they are not a big market. Your imagery will help really much!

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Comment from IrlJidel on 10 May 2017 at 17:40

re coverage and metadata - in the meantime is this an equivalent source to get coverage/vintage for the DigitalGlobe-Standard layer?

https://platform.digitalglobe.com/content/MapsAPI_Vintage-Leaflet.html#3/40.25/-10.55

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Comment from Zverik on 10 May 2017 at 17:43

where we have imagery available, it should all overzoom or oversample to maximum zoom. <...> My guess is you found an area where we haven't published imagery.

Ah, I've probably got it. The Premium layer falls back to the Mapbox imagery, which does not overzoom. Where there is a satellite photo special to that layer, it overzooms properly. Thanks!

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Comment from alexkemp on 13 May 2017 at 14:55

Gosh, but I was eager to try this out but, in the end, have very mixed feelings. Most of my time is spent adding houses (currently in Mapperley, Nottinghamshire). Whilst I'm grateful to have something to use to draw house outlines from, I've kept having satellite envy at how much sharper Google imagery is than Bing. No longer!

In my neck of the woods:–

  • Google is far sharper than Bing
  • Bing is sharper than DG
  • DG is sharper than Mapbox

But then...

  • Google is usually newer than Bing
  • Bing is sometimes newer than Google
  • DG is newer than Bing
  • Mapbox is newer than Bing

So, my search for sharper, newer satellite imagery continues (yet DG is providing much-needed, if blurry, imagery right now, for which many thanks).

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Comment from rorym on 16 May 2017 at 07:47

This is great! Some of it is newer imagery than what we had before (Bing & Mapbox), so I was able to add some new things. It's fantastic that we have another source for aerial imagery! 🙌🎉🎆

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Comment from joost schouppe on 18 May 2017 at 18:28

This is really massive gift. I've heard from happy people in the Congo and Bolivia, and even here in Belgium it's a great additional resource.

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Comment from Stereo on 20 May 2017 at 18:36

Thank you DigitalGlobe!

The premium imagery is great; it covers places in Ireland that weren't well covered by bing, or very badly. For example, Inishtrahull, off the coast of Donegal. It's also great to then georeference the old gsgs map

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Comment from Palolo on 22 May 2017 at 11:10

Having access to this imagery from DigitalGlobe is very nice.

The biggest problem I have with this is the lack of metadata: When was the imagery in a given area acquired? Here in Ethiopia we have some gaps in the nice Bing imagery, however, where both DigitalGlobe and Bing are at a suitable resolution it is important to compare the dates when each image was collected. There are places where it appears that DigitalGlobe is about 10 years out of date in this example, but that is just a guess.

One of the biggest strengths of OSM is the history file for each feature, without metadata from DigitalGlobe we are reducing the quality of the OSM data we produce.

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Comment from @kevin_bullock on 22 May 2017 at 15:40

thanks for all the feedback alexkemp, rorym, joost, Stereo!

Palolo, re: Metadata, we will make it available.

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Comment from Palolo on 23 May 2017 at 13:07

Thank you, knowing more information about the imagery will make it much more valuable.

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Comment from RespectableStreet on 21 September 2017 at 16:28

Kevin, your comment back in May said something about making metadata available in the coming weeks. A couple of days ago, I checked and still am not seeing dates. I know the best that the premium (vivid) service can offer is a date range. Will the standard service be able to provide specific dates, maybe with the exception of the landsat backfilled areas?

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