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#1 2009-12-13 13:46:24

om3g4
Member
From: Tirol, Austria
Registered: 2009-07-23
Posts: 29

Perth - Nearmap Aerial Imagery

Hi there,

i started mapping some parts of Perth with the high resolution nearmap imagery some days ago. the quality seems to be quite good yet it seems that the images are somehow not ortho-rectified correctly perhaps due to an inaccurate digital elevation model (DEM). when i started working on adding some houses and features yesterday, I recognized that a lot of houses suffered a shift (according to the underlying nearmap photos). Did they use a new DEM to recalculate the images?

Well actually I really love mapping australia right now, cause I think there is no other place around the world with that kind of high resolution image data available...


anyone else mapping near perth?


Greetings from Austria,
Julian

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#2 2009-12-16 00:01:25

mtrax
Senior Member
From: Canberra, Australia
Registered: 2008-05-20
Posts: 105

Re: Perth - Nearmap Aerial Imagery

I did see someone mention this last week or two in the OSM blog ..
BTW there seems to be alot of chatter on the "talk-au" mailing list too

Last edited by mtrax (2009-12-16 00:03:33)

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#3 2009-12-22 08:41:09

Re: Perth - Nearmap Aerial Imagery

om3g4 wrote:

i started mapping some parts of Perth with the high resolution nearmap imagery some days ago. the quality seems to be quite good yet it seems that the images are somehow not ortho-rectified correctly perhaps due to an inaccurate digital elevation model (DEM). when i started working on adding some houses and features yesterday, I recognized that a lot of houses suffered a shift (according to the underlying nearmap photos). Did they use a new DEM to recalculate the images?

You are mixing datums here, imagery is WGS84 (lat/lon), where as OSM rendered maps are spherical mercator (x,y)

Also the imagery as best as we can tell is mostly sub-metre accuracy, in some cases up to 5m but nearmap fixes that up on the next pass usually.

Nothing that I know of that is available to OSM'ers comes even close to that kind of accuracy (and resolution), if you do notice bad accuracy etc you should report it to nearmap so they can fix it up, check out the wiki for more details on the nearmap imagery.

Well actually I really love mapping australia right now, cause I think there is no other place around the world with that kind of high resolution image data available...

Actually Perth has the highest resolution NearMap imagery available, down to level 22, other cities are only level 21. You can actually see how train line switch points are set in Perth.

Last edited by JohnSmith (2009-12-22 08:43:33)

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