Has anyone tried to use the free New Zealand GeoTiff files from this source (LINZ)?
All I get is messages saying the file should be in contiguous planar data organisation (or words to that effect).

Dales.

Hi Dales,

Well, I had no problems with the NASA Landsat GeoTIFF files that I downloaded for Cyprus (sorry I can't remember the exact URL).

However, the download speed of the LINZ files at the moment is so slow that I'm not going to be able to try one today! :shock:

BTW have you worked out why the 1:50k GeoTIFF files which are mainly sea still seem to be so large (when the corresponding TIFF is quite small)?

Cheers, Alan.

Hi,

It could be worth watching the MM NZ forum although currently the only information appears to be that MM can import the LINZ files but they might need conversion by a PC Program (not identified). However, my tests suggest that's not the whole story:

Perhaps I should start by saying that I usually import maps in .PNG format because the resulting .QCT files are almost exactly the same size, which suggests that the QCT format is based on PNG. PNG uses non-lossy compression (except that MM only accepts a 256 colour palette) so the files can be relatively small.

However, MM can also import .TIF files, apparently with more than 256 colours (if present), which it presumably converts during import. But compression is optional with TIFF files so they can be quite large.

So, now back to the LINZ maps. There are four different formats and they seem to all behave differently: :?

The 1:250k GeoTIFF are the most obvious to try first, but as Dales reported above MM fails with the error message. Furthermore, Windows Picture Viewer and my versions of Paintshop Pro, Picassa, GPSU, etc. also fail to read the files so it seems to be rather a "difficult" format. Has anybody any ideas what might be able to read or convert it?

MM responds to the other three file formats with an "unrecognised format" error, but that's easy to fix, just remove one of the 'f's from the TIFF extension (to make .TIF). :) Then the files are correctly imported, but of course only the 1:50k GeoTIFF is actually calibrated.

To answer my own question in the post above, only the 1:50k TIFF files seem to be compressed, having sizes of about 1MB - 20MB, compared with the fixed (per type) sizes of 140MB - 220MB of the other three formats. So it might actually be quicker to download and manually calibrate the 1:50k TIFF files than to use the GeoTIFFs.

Manual calibration seems quite straighforward because the maps carry grid lines just like OS maps. But LINZ also seem to give plenty of data for calibration so perhaps somebody will suggest a suitable method or conversion tool. Cropping off the legend and other data from the TIFF maps can be done either in a graphics/photo package before calibration, or by using Map : Boundary to Route : Send Enclosed Route, etc.

Finally, although these maps have the same nominal scales as OS (1:50k and 1: 250k) maps, they actually appear about 18% larger within MM. The OS 1:50k maps have 200 pixels/km whilst the LINZ have about 236 pixels/km (intended to be printed on paper at 300 dpi).

Well, that seems to be the situation at present, perhaps we'll be able to refine the techniques as we did for the OS StreetView Opendata. ;)

Cheers, Alan.

Crikey, you've been busy!
Dabbling with the 250k GeoTiffs is as far as I got.
I've managed to view them in QuickTime Picture Viewer (but to no effect as I cannot zoom in at all).

Based on your findings, I might just set to on the 50K GeoTiffs instead, and get them downloaded. Good job I'm in no rush!

I think I'll sit back and wait for Greymane or the NZ forum to come up with some more tips on processing the 250k files into MemoryMap.

Cheers,

Dales.

Hi Dales,

I thought the 17GB download of the OS StreetView was rather heavy going, but the 450 x LINZ 50k GeoTIFF files amounts to over 60GB. :shock: However, they should compress/merge down to one or two .QCT files of <4GB if required.

I've successfully calibrated one of the 1:250k TIFF files but it seems a pity to have to download the same, unnecessary 75MB of border/legend with every map (and of course to do the manual calibration for each one). So let's hope that somebody comes up with a method to process the 1:250k GeoTIFFs.* ;)

Some of the compressed 1:50k TIFF files are much larger than I quoted previously, the largest so far about 70MB. It might be the proliferation of contour lines, or that some areas have a printed texture/screen which is likely to defeat a non-lossy compression algorithm.

I'm puzzled that Paintshop Pro reports >10,000 colours for what appears to be print masters. However, when merging samples together I see a slight variation particularly in the background "white". It doesn't affect the functionality, it just makes more obvious the joins where merges have taken place. Again, I don't know if it suggests that the sheets are actually scans, or if it is an artefact of the reduction from "thousands of colours" to less than the 256 required by MM. Or it might be an effect of the following trick which I used to reduce the download filesizes:

In general, I only downloaded alternate-numbered GeoTIFFs (e.g. only those with an odd-numbered row and column) and the remainder in the smaller, compressed TIFF format. Having imported all the georeferenced files into MM, it's only necessary to use : Convert boundary to Route , to create all the corner points required for calibrating the intermediate maps, and then for adding their boundaries. However, maybe I was unlucky that my first download attempt achieved only 6kB/sec (it was evening in NZ). My recent trials have been more rapid, so maybe the brute force download of all GeoTIFFs could be viable.

* BTW I note that you referred to Greymane from the old forum. I don't know if he, Ron and now USmmtech are all the same person, but suspect they might be? ;) At least we now know what Richard S. is doing :)

Cheers, Alan.

Yes, I do hope that somebody comes up with a method to process the 1:250k GeoTIFFs into MM.

I deliberately mentioned Greymane, to see if it produced any sort of reaction from abroad.

You've produced a wizard wheeze for calibrating the intermediate maps, I must say!

I seem to recall reading that LINZ apply a maximum of 4 files downloading at one time. I do mine overnight (as I get usage charges in the daytime) and the speeds are much faster than 6kb/sec, but it's tedious to wake up and be only 4 files further forward. I'll persevere with brute force and patience.

Dales.

Hi Alan,

All's working fine now.

I used freeware Orbit Downloader, with its scheduler, and I set Preferences..limits..always retry, so as to remedy the constant LINZ disconnections.

The topo50 GeoTiffs merged straight into 2 large files, fully geo-referenced and with search and 3D now enabled. [Edit: the geo-referencing of individual tiles is spot on. But after merging, the South Island is off a little - probably pulled about by the remote Chatham Island tile, which perhaps is best left separate].

The topo250 GeoTiffs took more work, once downloaded.
First I passed them through freeware DIMIN viewer, to solve the "contiguous planar" problem.
Then I used freeware libgeogui to Export a gtf file for each tif. I edited these in Notepad to swap all text between “Keyed Information:” and “ProjectionGeoKey” for the equivalent text from any of the topo50 files. I used the gui again to Embed the new metadata.

Phew!!

Dales.

Just an update. Teh GeoTiffs seem to import fine into memory map as they are on the http://www.linz.govt.nz/ or at least the 1:50k ones are showing fine to me. Just a shame they are 10 times the size of the qct files. Going to be a good few GB of downloads to get the whole of NZ!!

When you load the GeoTIFF into Memory-Map, it will create a QCT "copy" of the map. To find this QCT file, look under MAP > MAP LIST > REFRESH MAP LIST. At the bottom of the box is a MAP FOLDER button. The folder shown next to this button should contain the QCT version of the map. This QCT version should be significantly smaller than the TIFF file.