Manifold Community Site: Landsat image projections

RE: Landsat image projections

alancooper — Thu, 03 Jul 2008 08:40:11 GMT

I have become an enthusiastic Manifold user and apologise in advance if this topic has been covered in another thread. I have read so many threads that I am now overloaded and need a shortcut to solve my problem - hence this new thread.

I have successfully processed 18 full scenes and have got the results I wanted via band combinations and tweaking the contrast etc.

I need to remove the black margins of each scene so that they will overlap without the black showing. After reading many threads (and the training movies) I managed to remove the margin by selection and then to save the result as a new tiff with projection info. as well so that it can be loaded into ARCGIS.

Now don't start beating me up over the use of another GIS - I have to - the client demands it and the ulimate end user will be using ARCGIS.

BUT after removing the margin the projection information disappears/gets wrecked.

I know it is this process of removing the margin that is doing it as the original scene loads perfectly before the margin is removed.

I think the answer lies in the fact that I am removing pixels and not making them transparent and as I say the answer is already in the threads somewhere but I have lost a lot of time on this and need to catch up quickly.

TIA

RE: Landsat image projections

adamw — Thu, 03 Jul 2008 09:05:55 GMT

Do you mean that the original image loads into ArcGIS correctly, but the image with the margins removed does not? If so, after you trim the margins and export the image in Manifold, export the projection of the image as a PRJ file (open the image component, Edit - Assign Projection, click the Save to File button in the toolbar at the top of the projection dialog) and set the name of the PRJ file to coincide with that of the exported image file. This should solve the problem.

RE: Landsat image projections

danb — Thu, 03 Jul 2008 13:52:35 GMT

Adam,

I'm not 100% sure, but I don't think Arc uses prj files for anything other than drawings. I think ArcGIS uses an aux file as the equivalent of a prj file with images.

Anyone know for sure?

RE: Landsat image projections

volker — Fri, 04 Jul 2008 01:45:14 GMT

In the past i had the same problem. I mean i saved the projection

in an *.prj-File and rename it into *.tfw. Esri understand this.

But it`s a long time ago and i don`t find the files quickly, but

try this.

RE: Landsat image projections

pcardoso — Fri, 04 Jul 2008 05:46:00 GMT

ArcGIS do not uses prj for Raster files. I'm not sure now but I guess it is a aux file.

prj will be useless in this case if it cannot be changed to *aux* file.

RE: Landsat image projections

Nick Verge — Thu, 03 Jul 2008 15:13:29 GMT

Alan,

After you have cropped the black borders, why dont you mosaic the scenes in Manifolf (load scenes into a map object) then use tools | make image (select appropriate options) and create a single large image. This will obviously have a border, but this will not matter as now you will be able to export the mosaic as a large geotiff (or other file format eg .img) and inport it into ArcView. ( i assume ArcView does import geotiffs and .img)

RE: Landsat image projections

alancooper — Fri, 04 Jul 2008 00:59:46 GMT

Thanks for all this - I think the answer lies in re-attaching the projection back to the image. Manifold won't assign/change the projection after clipping so I guess it has lost the pixel/coord relationship.

I am going to try Adam's suggestion but before exporting into ARC I am going to try and bring it back into Manifold as a different file and ensure the projection works - then reexport.

I know there is a plug in for Photoshop to save the projection file and I have used this on another job but the 'try it' license has run out and it's a bit expensive just for this.

Is there any way to make the black transparent rather than remove altogether?

Alan

RE: Landsat image projections

alancooper — Fri, 04 Jul 2008 03:57:53 GMT

Would you believe it - there is a one click solution in ARCGIS.

One for the next release of Manifold?

RE: Landsat image projections

adamw — Fri, 04 Jul 2008 04:15:16 GMT

Sure. Post a suggestion through the usual channels (sales@manifold.net). For extra props, think about what you do and don't like about the feature as it is implemented in ArcGIS and post this too.

RE: Landsat image projections

Nick Verge — Fri, 04 Jul 2008 04:36:06 GMT

Alan,

Without wishing to state the obvious, why dont your export the images with their black borders and their georeferencing as geotiffs from Manifold and perform the clipping of the borders once they have been imported into ArcGIS.

I dont see why Manifold developers and its users should have to jump through hoops to compensate for the deficiencies of ArcGIS and the demands of its users. There are better things to be done.

RE: Landsat image projections

mdsumner — Fri, 04 Jul 2008 10:49:01 GMT

I'd like to *apologise in advance* and point out that no such request was made by anyone to compensate for any such deficiency. I furthur submit that it would be a challenge to find a more gracious query than the original submission made here, anywhere.

RE: Landsat image projections

Nick Verge — Fri, 04 Jul 2008 13:21:41 GMT

Mike,

Your offer to apologise in advance is very generous, but quite unnecessary as no criticism has been directed to Alan and i resent you implying i was making it. As usual you have entirely missed the main point and choosen to take issue with something that is only incidental to the subject of discussion. As you are having some difficulties, let me clarify for you.

In response to the suggestion that the problem, was an absence .aux files, i made the incidental point that Manifold developers should not create something to comepensate for the need of ArcGIS to have .aux files (a deficiency), since ArcGIS should be able to simply import and interpret geotiffs wherein the projection is embedded in the image file. However, I dont think the ability to create .prj and .aux files or any other external means of storing projection info of an image would solve Alan's problem as projection may not be the problem.

Assuming Alan is exporting tiffs with embedded projection info, the cause of Alan's problem may be the desire to be able to export an image with invisible deleted pixels. This is especially a problem for satellite remote sensing scene images because satellite RS scenes are not rectangular, but always parallelograms. With tiff files export of images with deleted pixels can only be done via use of a clipping path. I can confiorm that Manifold has no problem exporting and importing geotiffs that use a clipping path. However,

it may be that ArcGIS does not support import of (geo)tiffs that use a clipping path, or aleast ones exported from Manifold with one, or ones created by Manifold with one. I dont know. In an idea world ArcGIS would support both use of clipping paths and geotiffs.

I dont think Alan should be overly concerned about it, because it is an issue perculiar to his client's software.

However, this said, as i suggested earlier, the simplest possible solutions are either to mosaic the images in Manifold and export the result as one large image (doable, but awkward) Or to export the images from Manifold with the borders intact and the projection info in some human readable form, as .xml may be, then import these images into ArcGIS and delete the border pixels once in ArcGIS. Now it may that if the exports from Manifold are to be in geo(tiff) images will have to be imported into ArcGIS and the projection info added to each image from within ArcGIS (again awkward but not the end of the world)

RE: Landsat image projections

lionel_ — Fri, 04 Jul 2008 19:54:56 GMT

RE: Landsat image projections

alancooper — Sat, 05 Jul 2008 01:33:16 GMT

Gentlemen please!

It's Saturday morning, pouring with rain outside and I have a solution so I am catching up after the frustrations of last week.

Nick, I have done what you suggested - done all the donkey work in Manifold and imported into ARC where I remove the back borders.

Normally when I don't understand something or I can't work it out, I explain to my wife who knows nothing about maps what work problem I have. I therefore have to marshal my thoughts and try to put them in a coherent order & generally the answer pops out all by itself or by her asking the most obvious question - wood for trees and all that - alligators and swamps.

In posting my thread to the forum I almost got there myself but other user's experiences modified and extended the solution. Job done - a tick in the box - and a gold star for all respondents.

I work on my own for 98% of the time so it is great to have a virtual office of colleagues. But no fighting!

RE: Landsat image projections

ColinD — Sat, 05 Jul 2008 02:58:05 GMT

Alan, good that you have found a short-term solution but your problem has me puzzled. While I don't work with Arc anything I do need to send readable images and I know I have sent ecw's straight out of Manifold (no prj or the like) that have been used without problem in ArcGIS 9 whatever. I wonder why a straight GeoTIFF from Manifold could not be used? I suppose the header could not be read?

RE: Landsat image projections

alancooper — Sat, 05 Jul 2008 03:18:04 GMT

Hi Colin,

You are correct but it isn't working all the time. I too am puzzled and frustrated. I suspect it is me having messed around for so long I have wrecked the original projection as some scenes export and some don't.

So I am going back to square 1 and for those scenes that don't come through I will go back to original landsat bands and reimport just letting Manifold get on with it.