Image Service / Mosaic Dataset Overview Gaps

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06-07-2010 06:14 PM
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by Anonymous User
Not applicable
Original User: worstell

We have about 1000 tiled DEMs in GRID format. Each DEM source GRID is in the geographic coordinate system and has overlapping edges (6 pixels) on all sides to ensure that we have no gaps.  We are trying to make a seamless mosaic using the new mosaic dataset functionality in ArcGIS 10 and serve them using ArcGIS Server Image Extension.  We have 2 problems we cannot seem to resolve.

The first problem is with the overviews. Overviews tend to have small sliver gaps along some of the footprint boundaries.  If zoomed in far enough, the gaps go away (I assume because the primary raster is being used). When zoomed out, some small gaps seem to show up as shown in the attached image "gap.jpg".  

The second problem is related to on-the-fly projection.  As noted earlier, the source DEM tiles are in geographic coordinate system and the mosaic dataset was also defined as geographic. On-the-fly projection introduces large gaps at certain scales.  The attached graphic "gap-albers.JPG" is a mosiac dataset in geographic that is projected on-the-fly into Albers using ArcMap.  These types of artifacts make mosaic datasets unusable for any type of application.

Could someone provide some guidance for troubleshooting mosaic datasets and how to eliminate these gaps?

Thanks
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10 Replies
PeterBecker
Esri Regular Contributor
This is a know issue with a Beta version of 10. The issues should have been resolved in final.
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by Anonymous User
Not applicable
Original User: worstell

We were using the ArcGIS 10 Pre-Release version.

Are there any workarounds?

Thanks Peter.
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Kuang-YaoLee
New Contributor
We got the similar problem - a small sliver gap along the boundary line.


We have about 1000 tiled DEMs in GRID format. Each DEM source GRID is in the geographic coordinate system and has overlapping edges (6 pixels) on all sides to ensure that we have no gaps.  We are trying to make a seamless mosaic using the new mosaic dataset functionality in ArcGIS 10 and serve them using ArcGIS Server Image Extension.  We have 2 problems we cannot seem to resolve.

The first problem is with the overviews. Overviews tend to have small sliver gaps along some of the footprint boundaries.  If zoomed in far enough, the gaps go away (I assume because the primary raster is being used). When zoomed out, some small gaps seem to show up as shown in the attached image "gap.jpg".  

The second problem is related to on-the-fly projection.  As noted earlier, the source DEM tiles are in geographic coordinate system and the mosaic dataset was also defined as geographic. On-the-fly projection introduces large gaps at certain scales.  The attached graphic "gap-albers.JPG" is a mosiac dataset in geographic that is projected on-the-fly into Albers using ArcMap.  These types of artifacts make mosaic datasets unusable for any type of application.

Could someone provide some guidance for troubleshooting mosaic datasets and how to eliminate these gaps?

Thanks
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by Anonymous User
Not applicable
Original User: eendrulat

I'm having the same problem where slivers are generated in the overview files (see attached screenshot) I used the default settings for creating the overview files, using ArcGIS Server/Desktop SP1. 

It appears this problem wasn't corrected in the final release, are there any suggestions on how to avoid this?

Thanks,
Erik
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larryzhang
Regular Contributor
From my practices, this thread has two different issues, which are very likely caused by two reasons:

1. Not shrinking, when running toolset of the 'building footprints'. Or not define NOData before running the 'building footprints'. In fact, if not shrinking, saying Post # 5 in this thread,  BLACK artifacts along borders of original imagery were not removed and may be visible in mosaic dataset;

2. very limited overlaps among tiles of ' processed sources", when doing the following operations:

�?� not shrinking properly, when running toolset of the 'building footprints';  (if shrinking too much, WHITE gaps may appear in mosaic datasets);

�?� in many areas with over 30 degree North, you may also face this issue like the following cases:

            A. there are big changes between two projection systems (that is, in mosaic dataset vs. data sources), for example, geodetic (lat & lon) vs.  Lambert Conformal, etc;

            B. sometimes, even though there are no  artifacts  in mosaic dataset, you still can see it when you load image service into ArcMap, which is using a different projection system (on-the-fly projection).

For solutions to very limited overlaps among tiles of 'processed sources', please refer to the attached Doc.
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by Anonymous User
Not applicable
Original User: eendrulat

I've had similar problems with gaps appearing in my mosaic dataset and subsequently opened a trouble ticket with Esri to try to resolve it.

I was told that this error (at least the one that I was having), has been given
NIM060205 "Mosaic dataset has slivers/gaps in overviews when the data frame is in a different projection than the mosaic dataset.",
and that this bug will not be fixed until 10.1.
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SaiDivya
New Contributor II
Hi Bruce,
Did you find solution to your 'Dem with a big slant gap (Fig1: gap-albers)'?
I am facing the same problem. I am also using albers projection. I tried on 9.3 and also on ArcGIS 10.0. Neither did give good solutions.
Please let me know if you find any solution. Many experts suggested to do in geodatabase and it also failed.
Please help me to fix this problem.
Thanks in advance
Raj




We were using the ArcGIS 10 Pre-Release version.

Are there any workarounds?

Thanks Peter.
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by Anonymous User
Not applicable
Original User: jbswain

There is a fix for this at service pack 3 for ArcGIS 10, for more information on the bug report that is addressed and to track it, I recommend creating a Support Incident.
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SaiDivya
New Contributor II
Hi
Thank you very much for the email. I will ask my admin people to install service pack 3.
Can you please send the link to create a support incident?
I feel this is very important aspect that ESRI need to look into it and fix it. I never had problem in 9.1.
By the way, I am working on University machine and if if asks the global a/c what do I need to fill?
Thanks
Raj
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