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Re: [Paparazzi-devel] log file UTM to WGS84 convert question

From: Gautier Hattenberger
Subject: Re: [Paparazzi-devel] log file UTM to WGS84 convert question
Date: Tue, 05 Aug 2014 11:56:25 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20131103 Icedove/17.0.10


I have tested a few online converters for your UTM coordinates:
39.502741,                  116.50624594826415
39.50274,                    116.50625
39.50274153051662,  116.50624594824883
-> they seem to agree

pprz was
39.502822146,            116.506218394
perl was
39.5046274995347,    116.506245384612
-> they are both different, but your latitude is really far compared to pprz

I think the error comes from the geodetic model, we are using WGS84 and you have set Clarke1880. Change the first parameter of the utm_to_latlong from 5 to 23 and try again.


Le 04/08/2014 20:36, afishindouban a écrit :
I use perl to make convert, and result is different to the PPZ log plotter
save to CVS latlong value. the different is always around tens meters. Its
really strange.

Can you help me to verified what is wrong ?
for example.

this is one msg in data file.
1832.0000 3 DC_SHOT 309 45754908 437268512 283.967987 50 -15 20 1735 1706

PPZ log plotter CVS latlong output is lat 39.502822146, long 16.506218394

But if you use Perl Geo::Coordinates::UTM
to convert.
Perl file:

#To use the Geo::Coordinates::UTM module first you must install it, see
eval {#use the require and import instead of 'use Geo::Coordinates::UTM;'
       #so that we can print an error message
       require Geo::Coordinates::UTM;
       import  Geo::Coordinates::UTM;
} || die("
Cannot load Geo::Coordinates::UTM --
please execute:
   perl -MCPAN -e 'install Geo::Coordinates::UTM'

my $utm_x = 457549.08;
my $utm_y = 4372685.12;
my $utm_z = "50S";

print "Convert \$utm_x, \$utm_y, \$utm_z =$utm_x, $utm_y, $utm_z\n";
my ($lat, $lon) = utm_to_latlon(5, $utm_z, $utm_x, $utm_y);
print "Result \$lat, \$lon=$lat,$lon\n";

the result is

Convert $utm_x, $utm_y, $utm_z =457549.08, 4372685.12, 50S
Result $lat, $lon=39.5046274995347,116.506245384612

You can see Lat and Long is different, and the distance of of the result is
about tens meters.

Where is the mistake ??? Please try to use this perl script to convert any
UTM address . to compare with ppz log plotter output.


Andreas wrote
Hi Kevin,

the letter for the latitudonal 8-degree band (T, R or S) may be
calculated after converting UTM to WGS84. It is insignificant for that,
since the utm_y is always the distance from the equator. For the utm_x
value where you need the zone number (e.g. 50) this is different since
it is the distance for the central meridian which depends on the zone.
The letter describing the latitudonal band is just cosmetics. You can
determine it after conversion to geographical coordinates:

the letters are "CDEFGHJKLMNPQRSTUVWXX" from 80 deg south in increasing
order for each 8-deg-band. However there are exceptions over
Scandinavia. May be better use a tool like:

linux pakage: proj-bin


Am 07.07.2014 03:17, schrieb afishindouban:
Hi everyone

sorry for bother you, I have a confuse about log file pos covert.

for example one line in a log file could be

130.5000 3 GPS 3 45628136 437386560 2918 20626 5 -6 1799 368074000 50 28

so the utm_x=45628136 utm_y=437386560 utm_zone=50, but it should say 50T,
50R or 50S for I can use UTM2WGS84 convertor. How can I get this
by a log file ?

Please help me. thanks a lot.


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