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<p>Hi, although I use 3" hgt files, <font size="2"><span style="font-size:11pt;">3312 looks much more detailed than
<font size="2"><span style="font-size:11pt;">9942?</span></font></span></font></p>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>Van:</b> mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> namens Gerd Petermann <GPetermann_muenchen@hotmail.com><br>
<b>Verzonden:</b> zaterdag 23 december 2017 03:33:30<br>
<b>Aan:</b> Development list for mkgmap<br>
<b>Onderwerp:</b> [mkgmap-dev] WG: r4015 in dem-tdb branch implements --x-overview-dem-dist</font>
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<div class="PlainText">Hi!<br>
I've just noticed that I replied to Minko instead of the list. Please see below.<br>
<br>
Gerd<br>
<br>
________________________________________<br>
Von: Gerd Petermann <gpetermann_muenchen@hotmail.com><br>
Gesendet: Samstag, 23. Dezember 2017 12:04<br>
An: lig fietser<br>
Betreff: AW: [mkgmap-dev] r4015 in dem-tdb branch implements --x-overview-dem-dist<br>
<br>
I am not sure what to think about that.<br>
When you use 3'' hgt files (size is ~2.8MB) the resolution in that data is 2^32/(360 * 1200) ~ 9942.<br>
When you use 1'' hgt files (size is ~26MB) the resolution in that data is 2^32/(360 * 3600) ~ 3314.<br>
The current implementation in mkgmap interpolates the values found in the hgt file. It assumes<br>
continous slope between two points at the same lat, so e.g. if one is 123 and the other is 135,<br>
it assumes that a point in the middle is at 129.<br>
I assumed that the Garmin algo does something similar when calculating the heights, but maybe it<br>
doesn't.<br>
<br>
I did not yet try to find out the best values for dem-dists, so it would be good to hear about results.<br>
<br>
Gerd<br>
<br>
________________________________________<br>
Von: lig fietser <ligfietser@hotmail.com><br>
Gesendet: Samstag, 23. Dezember 2017 11:45:21<br>
An: Gerd Petermann<br>
Betreff: Re: [mkgmap-dev] r4015 in dem-tdb branch implements --x-overview-dem-dist<br>
<br>
Thanks Gerd, the value of 3312 works much better now!<br>
<br>
________________________________<br>
Van: Gerd Petermann <gpetermann_muenchen@hotmail.com><br>
Verzonden: zaterdag 23 december 2017 02:36:32<br>
Aan: lig fietser<br>
Onderwerp: AW: [mkgmap-dev] r4015 in dem-tdb branch implements --x-overview-dem-dist<br>
<br>
Hi Minko,<br>
<br>
to convert the parms for BuildDEMFile you have to multiply by 2^32/360 :<br>
0.00027761 * 2^32/360 ~ 3312.<br>
<br>
Gerd<br>
<br>
________________________________________<br>
Von: lig fietser <ligfietser@hotmail.com><br>
Gesendet: Samstag, 23. Dezember 2017 11:30:20<br>
An: Gerd Petermann; Development list for mkgmap<br>
Betreff: Re: [mkgmap-dev] r4015 in dem-tdb branch implements --x-overview-dem-dist<br>
<br>
Hi Gerd,<br>
Thanks for the good work to implement DEM into mkgmap!<br>
I have tested a few tiles, I noticed that BuildDEMFile with--dlon=0.00027761 has a much more detailed relief than the default values x-dem-dists=5520, 16560, 44176, 88368 How can I get the same results as with dlon=0.00027761?<br>
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