Hi Gerd Thanks for the detailed explanations. ' if you want more precision and map size doesn't matter half of it ' I'm not quite sure how halving these values produce greater precision for resolution 24.  Interestingly , you mention 1664 . One of my topos has 1648  as in   1648,3312,13248,53024  Nick On 31/01/2018 11:03, Gerd Petermann wrote:

Hi Minko,

I'd also like to know a good rule how to calculate the dem-dists values.

Again the basic formulars: Typical hgt formats use a raster with either 1200 (3'') or 3600 (1'') points/degree as resolution. The corresponding resolutions for DEM are 2^32/(1200*360) ~ 9942 or 2^32(3600 * 360) ~ 3314

It is quite obvious that the first value in dem-dists depends on the resolution of the input hgt file(s). My understanding is that you might use a value near the hgt resolution or maybe - if you want more precision and map size doesn't matter - half of it, so 3'' hgt means dem-dist ~ 9942 (or 9942/2 = 4971) 1'' hgt means dem-dist ~ 3314 (or 3314/2 = 1657) Since mkgmap now rounds these values to multiples of 16 you get 2^32/(1200*360) ~ 9942 -> 9936 rounded 2^32/(1200*360) / 2 ~ 4971 -> 4976 rounded 2^32/(3600*360) ~ 3314 -> 3312 rounded 2^32/(3600*360) / 2 ~ 1657 -> 1664 rounded

These are the values for resolution 24. What still seems unclear is how you calculate the values for lower resolutions. Up to now I see no reason to duplicate data with e.g. dem-dists=3312,3312,... but I see this in Arndts "Speichenkarte" which uses resolution 23 for level 1.

I tried some different values on my Oregon 600 and I think the hill shading is not very useful on the device. Maybe that's the reason why the setting Map->Advanced Setup->Shaded relief->Auto means that hill shading is not used unless you zoom out to 5km?

I also tried with only one or two DEM levels, e.g. --dem-dists=1664,3312 or just --dem-dists=3312 It works, the device just uses the DEM from the basemap when you zoom out to e.g. 500 m. The problem: The basemap has a very poor DEM resolution, so it looks wrong when hills suddenly disappear while zooming out.

My current compromise for high precision with 1'' hgt input and default style: 1664,9936,26512,53024

Gerd

________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von lig fietser <ligfietser@hotmail.com> Gesendet: Mittwoch, 31. Januar 2018 09:48 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] Please help with news about new DEM options

Yes, it would be helpful if we mention where we can get the hgt files, a few examples of the dem-dist values and an explanation how to calculate it. This information is already there but mentioned in the many updates of the branch versions.

I use http://www.javawa.nl/srtm/index.php?lang=nl because it has a good overview map, the disadvantage is that you need to download every single tile manually and not in one big download. Maybe there are better alternatives?

---------------------

Gerd wrote:

Hi all,

with r4093 I've merged the dem-tdb branch into trunk. I think it would be good to mention this in the "Latest news" on [1] , maybe with one or two screen shots, but I have no idea how to write this "from a users view". Do we need a how-to that describes the sources for hgt files and maybe more about the new options? It would be great if somebody could help with that.

Gerd

[1] http://www.mkgmap.org.uk/ _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev

Thanks Gerd One certainly gets more of the lumps and bumps with a distance of 1664 Nick On 31/01/2018 13:20, Gerd Petermann wrote:

Hi Nick,

well, Andrzej reported that this oversampling might improve precision. My understanding is that it reduces the error that is added by interpolation.

For sure it adds a lot of bytes to the img file, so one has to find out what is more imprtant.

Gerd

________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von osm@pinns <osm@pinns.co.uk> Gesendet: Mittwoch, 31. Januar 2018 13:32 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] Please help with news about new DEM options

Hi Gerd

Thanks for the detailed explanations.

' if you want more precision and map size doesn't matter half of it'

I'm not quite sure how halving these values produce greater precision for resolution 24.

Interestingly , you mention 1664 .

One of my topos has 1648 as in

1648,3312,13248,53024

Nick

On 31/01/2018 11:03, Gerd Petermann wrote:

...

Hi Minko,

I'd also like to know a good rule how to calculate the dem-dists values.

Again the basic formulars: Typical hgt formats use a raster with either 1200 (3'') or 3600 (1'') points/degree as resolution. The corresponding resolutions for DEM are 2^32/(1200*360) ~ 9942 or 2^32(3600 * 360) ~ 3314

It is quite obvious that the first value in dem-dists depends on the resolution of the input hgt file(s). My understanding is that you might use a value near the hgt resolution or maybe - if you want more precision and map size doesn't matter - half of it, so 3'' hgt means dem-dist ~ 9942 (or 9942/2 = 4971) 1'' hgt means dem-dist ~ 3314 (or 3314/2 = 1657) Since mkgmap now rounds these values to multiples of 16 you get 2^32/(1200*360) ~ 9942 -> 9936 rounded 2^32/(1200*360) / 2 ~ 4971 -> 4976 rounded 2^32/(3600*360) ~ 3314 -> 3312 rounded 2^32/(3600*360) / 2 ~ 1657 -> 1664 rounded

These are the values for resolution 24. What still seems unclear is how you calculate the values for lower resolutions. Up to now I see no reason to duplicate data with e.g. dem-dists=3312,3312,... but I see this in Arndts "Speichenkarte" which uses resolution 23 for level 1.

I tried some different values on my Oregon 600 and I think the hill shading is not very useful on the device. Maybe that's the reason why the setting Map->Advanced Setup->Shaded relief->Auto means that hill shading is not used unless you zoom out to 5km?

I also tried with only one or two DEM levels, e.g. --dem-dists=1664,3312 or just --dem-dists=3312 It works, the device just uses the DEM from the basemap when you zoom out to e.g. 500 m. The problem: The basemap has a very poor DEM resolution, so it looks wrong when hills suddenly disappear while zooming out.

My current compromise for high precision with 1'' hgt input and default style: 1664,9936,26512,53024

Gerd

________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von lig fietser <ligfietser@hotmail.com> Gesendet: Mittwoch, 31. Januar 2018 09:48 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] Please help with news about new DEM options

Yes, it would be helpful if we mention where we can get the hgt files, a few examples of the dem-dist values and an explanation how to calculate it. This information is already there but mentioned in the many updates of the branch versions.

I use http://www.javawa.nl/srtm/index.php?lang=nl because it has a good overview map, the disadvantage is that you need to download every single tile manually and not in one big download. Maybe there are better alternatives?

---------------------

Gerd wrote:

Hi all,

with r4093 I've merged the dem-tdb branch into trunk. I think it would be good to mention this in the "Latest news" on [1] , maybe with one or two screen shots, but I have no idea how to write this "from a users view". Do we need a how-to that describes the sources for hgt files and maybe more about the new options? It would be great if somebody could help with that.

Gerd

[1] http://www.mkgmap.org.uk/ _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev

---

mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev

Hi Carlos, thanks again. Seems I need new glasses when I look at all those typos :O I like the introducing chapter about DEM, but I don't fully agree reg. dem-dists: "Reasonable values for the highest resolution are somewhere between 1648 and 5520 for 1'' hgt input files (3312 is often used), and 9942 for 3'' hgt input files." Since 9942 is close to the resolution of the 3'' hgt I think 5520 is also suitable for a 3'' file. Maybe we should add that 1'' means ~ 3314 distance and 3'' means ~ 9942 and that the 1st dist value should not be much smaller than 50% of that distance? Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Carlos Dávila <cdavilam@orangecorreo.es> Gesendet: Freitag, 2. Februar 2018 22:32 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] Please help with news about new DEM options El 30/01/18 a las 09:41, Gerd Petermann escribió:

Hi all,

with r4093 I've merged the dem-tdb branch into trunk. I think it would be good to mention this in the "Latest news" on [1] , maybe with one or two screen shots, but I have no idea how to write this "from a users view". Do we need a how-to that describes the sources for hgt files and maybe more about the new options? It would be great if somebody could help with that.

Gerd

[1] http://www.mkgmap.org.uk/

Attached patch is not exactly what you asked for, but I hope it adds some useful information about DEM.

Having read the explanation of --dem-dists I think that the default for when the option is not provided needs to be changed. The explanation says "mkgmap tries to determine a reasonable value based on the resolution found in the *.hgt files", but it also says "for gps devices you need one for each resolution given with the --levels option". It seems to me the default behaviour should be to produce a map suitable for GPS devices, and hence it should determine a set of values. I suggest renaming this option --dem-distances as its meaning is clearer. Also I suggest capitalising GPS. I suggest renaming --overview-dem-dist to --dem-overview-distance so that all the DEM options begin with --dem. I also suggest moving the explanation to immediately after --dem-dists. As --overview-levels allows multiple values, does the DEM overview level also allow multiple levels (in which case the name needs to be --dem-overview-distances)? If not, we need a mention why only a single value is needed. For the --dem-poly option, I suggest adding a mention that the areas.poly file produced by splitter can be used. Hope this helps, Mike -----Original Message----- From: Carlos Dávila [mailto:cdavilam@orangecorreo.es] Sent: 02 February 2018 21:33 To: mkgmap-dev@lists.mkgmap.org.uk Subject: Re: [mkgmap-dev] Please help with news about new DEM options El 30/01/18 a las 09:41, Gerd Petermann escribió:

Hi all,

with r4093 I've merged the dem-tdb branch into trunk. I think it would be good to mention this in the "Latest news" on [1] , maybe with one or two screen shots, but I have no idea how to write this "from a users view". Do we need a how-to that describes the sources for hgt files and maybe more about the new options? It would be great if somebody could help with that.

Gerd

[1] http://www.mkgmap.org.uk/

Attached patch is not exactly what you asked for, but I hope it adds some useful information about DEM.

Hi Gerd, I think that it is better to get a rational set of option names than worry about causing confusion due to minor changes. I would think there are only a handful of people using the DEM options at the moment, and I don't believe anyone who is not on the development list will be using them yet. If there is anyone who has picked up the options and is not on the development list, they will get an error message saying they have an unrecognised option and will very quickly sort out what has changed. I think it needs to be explained that only one DEM overview is needed, despite the fact that there may be multiple overview levels. Arndt Röhrig suggested to me that the splitter output poly file be used when I asked for a DEM Noddy Guide - if it makes more sense to use the one provided as input to splitter then I suggest that be added to the documentation instead, and possibly suggesting that the areas.poly from splitter should not be used. I have been using areas.poly, but have not tried with no --dem-poly option, so don't know whether it makes any difference. Is this option intended to be used only when you want areas of the map to not have DEM data? If that is the case, then the documentation needs to say that in general this option need not be used (presumably using the one provided as input to splitter will also have no effect in that case). The wording of "If not given, the DEM data will cover the full tile area" is not sufficiently clear to me. Cheers, Mike Regards, Mike -----Original Message----- From: Gerd Petermann [mailto:gpetermann_muenchen@hotmail.com] Sent: 03 February 2018 08:52 To: Development list for mkgmap <mkgmap-dev@lists.mkgmap.org.uk> Subject: Re: [mkgmap-dev] Please help with news about new DEM options Hi Mike, - I also wondered if mkgmap should produce more DEM levels when --dem-dists is missing, the problem is that I was unsure about the values to use. - I like your suggested option names but I'd prefer not to change the options this late to avoid confusion. - There is only one overview-dem-dist because MapSource and Basecamp don't need more and the overview map is not used on the GPS. - Can you explain what effect you expect when you use --dem-poly with the areas.poly from splitter? My understanding is that this should not change the map, at least not visibly, as the areas.poly simply describes the outline of the rectangular tiles. On the other hand it makes sense to use the poly file that was used as input for splitter. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Mike Baggaley <mike@tvage.co.uk> Gesendet: Samstag, 3. Februar 2018 09:29 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] Please help with news about new DEM options Having read the explanation of --dem-dists I think that the default for when the option is not provided needs to be changed. The explanation says "mkgmap tries to determine a reasonable value based on the resolution found in the *.hgt files", but it also says "for gps devices you need one for each resolution given with the --levels option". It seems to me the default behaviour should be to produce a map suitable for GPS devices, and hence it should determine a set of values. I suggest renaming this option --dem-distances as its meaning is clearer. Also I suggest capitalising GPS. I suggest renaming --overview-dem-dist to --dem-overview-distance so that all the DEM options begin with --dem. I also suggest moving the explanation to immediately after --dem-dists. As --overview-levels allows multiple values, does the DEM overview level also allow multiple levels (in which case the name needs to be --dem-overview-distances)? If not, we need a mention why only a single value is needed. For the --dem-poly option, I suggest adding a mention that the areas.poly file produced by splitter can be used. Hope this helps, Mike -----Original Message----- From: Carlos Dávila [mailto:cdavilam@orangecorreo.es] Sent: 02 February 2018 21:33 To: mkgmap-dev@lists.mkgmap.org.uk Subject: Re: [mkgmap-dev] Please help with news about new DEM options El 30/01/18 a las 09:41, Gerd Petermann escribió:

Hi all,

with r4093 I've merged the dem-tdb branch into trunk. I think it would be good to mention this in the "Latest news" on [1] , maybe with one or two screen shots, but I have no idea how to write this "from a users view". Do we need a how-to that describes the sources for hgt files and maybe more about the new options? It would be great if somebody could help with that.

Gerd

[1] http://www.mkgmap.org.uk/

Attached patch is not exactly what you asked for, but I hope it adds some useful information about DEM. _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev