Merging (aerial photo) maps

MrT · Posted: Fri Jan 23, 2004 9:10 am Post subject: Merging (aerial photo) maps

When two aerial maps are merged that are vertically adjacent, the merged map always has part missing. On the seam of the maps, the maps meet at each end but in the middle there is a white gap of some 250 metres of missing land. This information that is missing from the merge comes from the lower of the two maps and is present on the original, ie the gap is not due to a projection distortion but missing data from the merge.

If you have Region 4 Photo take a look at OS grid TL65,98 it seems a little odd.

MikeB · Posted: Wed Feb 04, 2004 8:31 pm Post subject:

Merging maps is not something I have needed to do until this week. The OS maps always seem to give me the right coverage in the middle of the map area.

Things changed this week when I needed to merge 2 sections of Nautical charts in the Florida Keys. These merged perfectly.

I suspect (but can't prove) that what is happening is that the Aerial Photos have blank calibrated collars which MM sees as being part of the map. When it overlays them and matches them up the blank collar is clearly visible. Does your blank area extend all the way across the join? If it does then this would be pretty conclusive.
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Mike Barrett

MrT · Posted: Mon Feb 16, 2004 10:26 am Post subject: Blank Area

The aerial photos meet at the ends of the join but there white gap is in the middle.

A horizontal merge works OK.

According to memory map support the aerial photos are not meant to be merged.

TigerMoff · Occasional Visitor Joined: Oct 22, 2003 Posts: 20

You will find that it is due to the curvature of the earth that there a gaps between the tiles (not missing sections). Memory map gets the top and bottom ends of the tile and joins them thus making a bow in the middle. This only happens in the 2004 OS edition since the calibration function was removed.

MrT · Posted: Mon Feb 23, 2004 8:07 pm Post subject:

TigerMoff · Occasional Visitor Joined: Oct 22, 2003 Posts: 20

Im sorry but I think we will have to agree to disagree on this one then. I have been able to merge maps with out any problem in the 2003 software using the 2003 maps.

MrT · Posted: Sun Feb 29, 2004 5:27 pm Post subject: TigerMoff

Can you let me know which Aerial Photo tiles you merged (vertically) so that I can try it with 2003? It may be that it only affects certain tiles?

Horizontal photo tile merges or maps where boundaries overlap by 20km have no problem.

TC · Posted: Wed Mar 03, 2004 1:02 pm Post subject:

I also tried merging maps together and I am not impressed.

I have 2003 and tried merging UK(OS) regions (south-west, south wales - 1 and 3 I think) and got a big white gap. Yes I think the the map projection UTM is not applied correctly. It looks like on region gets the projection but the other is treated like a rectangular bitmap. In fact MM in my experience only realy likes dealing with one of anything e.g. one map (can be displayed) one elevation model (can be displayed) one places names.

I haven't tried this but I think if your meger maps successfully you will NOT get a merged elevation model or place name database. I'd like to be proved wrong.

Having said this I'd would like to say the I really like MM - it's by far and away better that Fugawi.

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