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Georectifying an historical aerial photo

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#1
marylooh

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Hi there,

I was wondering if anybody has experience with rectifying oblique aerial photographs? I have tried to rectify aerial photos from 1946 in ArcGIS using at least 20 control points and a third-order polynomial transformation. The result was not very satisfying (quite distorted in some areas after georectifying), so I've tried to rectify only parts of it at a time which looks better. I will still need to mosaic them together later. Also, is ERDAS a better program to do georeferencing?

Any advise to deal with situations like this is much appreciated.

Thanks,
Maria

#2
Kalai Selvan

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When you say Oblique aerial photograph, do you mean you are working on a Cross section map, which has "Azimuth values too?...Coz i remember working on cross sections, which haD similar requirement..

Cool!!
GISGURU

I was wondering if anybody has experience with rectifying oblique aerial photographs?

Thanks and Regards
Kalai Selvan


#3
Esther Mandeno

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Hello Marylooh,

I do not have experience directly with oblique historic aerial photos, only with standard aerial photos. And yes, it's a pain to geo-reference 'em. I can't imagine trying to do oblique images!

With that said, do you have spatial analyst? Or image analyst? I am running 9.2 with spatial analyst and when I geo-reference historic photos I often use way more than 20 points and I use the spline transformation option. The spline option "forces" the image to your control points. It works much better than the thrid-order polynomial transformation, at least for my images. I was recently working on another person's machine that had only an arcview license and no spatial analyst and they didn't have that geo-reference spline transformation option. If you only have one image to geo-reference and if you can export as many control points to a text file and forward both to me, I can geo-reference the image for you if you don't have access to spatial analyst. Alternatively, if you only have one to do, you can installed the evaluation copy of spatial analyst and try the spline option. At least, that way you would know if you suits your needs and whether it's worth it to go out and buy.

Good luck!
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Esther Mandeno
Life is like riding a bicycle. To keep your balance you must keep moving. - Albert Einstein

#4
Robert2009

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Hello Marylooh,

I do not have experience directly with oblique historic aerial photos, only with standard aerial photos. And yes, it's a pain to geo-reference 'em. I can't imagine trying to do oblique images!

With that said, do you have spatial analyst? Or image analyst? I am running 9.2 with spatial analyst and when I geo-reference historic photos I often use way more than 20 points and I use the spline transformation option. The spline option "forces" the image to your control points. It works much better than the thrid-order polynomial transformation, at least for my images. I was recently working on another person's machine that had only an arcview license and no spatial analyst and they didn't have that geo-reference spline transformation option. If you only have one image to geo-reference and if you can export as many control points to a text file and forward both to me, I can geo-reference the image for you if you don't have access to spatial analyst. Alternatively, if you only have one to do, you can installed the evaluation copy of spatial analyst and try the spline option. At least, that way you would know if you suits your needs and whether it's worth it to go out and buy.

Good luck!


Yes, I totally agreed with Esther . I had the same thing a couple of weeks ago and the best method is to do as much control points as you can. I find that using the spline works much better than other options and works very well.
I did mine a couple of weeks ago and the georeferenced images I exported from pdf files of a very old CAD from
the military area. By the way, I use ArcGIS 9.2 SP6. I find using Georeferencing toolbar in ArcGIS is better than
ERDAS because I remember using ERDAS and it was tough to do.

Good Luck,

Robert
USDA- NRCS
Las Cruces Soil Survey
Las Cruces, NM 88011

#5
marylooh

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Thanks a lot, Esther and Robert. Just saw your entries now.. it's been awhile, but still dealing with the same issues, so your comments are very useful, even a year later!

#6
Jimbob

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I have been working with oblique photos for some time and ca tell you that they do not rectify (or warp) very well. Depending on how 'oblique' they are, above ground features (such as houses and trees) stretch out and looked distorted.

The best way to display an oblique photo is to view it and fully georeferenced photo, but not warped. The photos is displayed using it's exterior orientation.

I've used a display program called Flyeye.ca (ArcGIS plugin) for displaying my coastline air photos, but there are several image viewing programs available.

Good luck :)




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