[resolved] Give a layer an shift / offset via .AQX

[jidanni]

I need to shift / offset a layer in my .AQX file.
I want to move it a few meters (or DMS) southeast, as seen:

20210427T024317.jpg

(60.5 KiB) Not downloaded yet

Can I somehow add a tweak via some
https://www.alpinequest.net/en/help/v2/ ... parameters
in <zoom-levels ...>
maybe in <server><...{$z}/{$y}/{$x} ?
I.e., y=real y but with a false input of real y minus .000123 degrees of latitude etc.? Thanks!
P.S., the map server is owned by enemy troops. Any contact (asking them to fix the map) would
result in world destruction so I am sure there is a way to just fake it via parameter recompilation.

[jidanni]

Maybe if I tried these two, with just a few meters...

Code: Select all

<projection-offset-x>-450000.0</projection-offset-x><!-- optional, default is 0 -->
<projection-offset-y>-800000.0</projection-offset-y><!-- optional, default is 0 -->

[jidanni]

In http://forum.psyberia.net/viewtopic.php?t=999 I found

Code: Select all

       <projection-name>mercator</projection-name>
        <projection-geoid>sphere</projection-geoid>
    <projection-origin-x>0</projection-origin-x>
        <projection-origin-y>0</projection-origin-y>
        <projection-factor-x>nb_tiles / 360</projection-factor-x>
        <projection-factor-y>nb_tiles / 360</projection-factor-y>
        <projection-offset-x>nb_tiles / 2</projection-offset-x>
        <projection-offset-y>nb_tiles / 2</projection-offset-y>

So maybe as the layer is .../EPSG:3857/... I can do ...?

[jidanni]

In viewtopic.php?t=2616#p10113 we see:

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   <projection-false-origin-x>-203224.0</projection-false-origin-x>
    <projection-false-origin-y>5429184.0</projection-false-origin-y>

[Psyberia-Support]

Hi Dan,

In fact you can use those tags to shift your map:

Code: Select all

<projection-false-origin-x>10.0</projection-false-origin-x>
<projection-false-origin-y>10.0</projection-false-origin-y>

Those tags must be inside the "<zoom-levels> ... </zoom-levels>" tags, not outside.

The values are expressed in meters, but if you use the default map projection (mercator), depending on where you are on the Earth the values will not exactly be meters.

[jidanni]

OK! And I think I figured out exactly what the difference is:
https://en.wikipedia.org/wiki/Longitude ... _longitude
I.e., the false Y stays the same. But the false X,, let's say 10 meters at the equator, will become around 9 meters around the Tropic of Cancer. Therefore if one wants 10 meters at the Tropic of Cancer one has to specify 11 meters. I got it!

And indeed, I found that specifying positive numbers indeed moves the layer in question Northeast and not the map underneath it thankfully.

Okay, as this tag pair is not documented, I guess this discussion will have to be its document for now.

[jidanni]

OK I made a shell script that runs on Android to adjust the offset dynamically:

Code: Select all

case $1 in
    a) #shift AQX
	m=$1
	shift
	set -e
	if test $# -ne 2; then echo 1>&2 $0: Usage: $m X Y; exit 86; fi
	for i do
	    case $i in
		*[!-0-9]*)
		    echo 1>&2 $0: $m: $i: [-]digits only.
		    exit 81
		    ;;
	    esac
	done
	: ${aqx=/sdcard/Android/data/net.psyberia.offlinemaps/files/datastore/custom-maps/dan01.aqx}
	if ! test -f $aqx; then echo 1>&2 No $aqx.; exit 87; fi
	pfo=projection-false-origin
	cp $aqx $aqx.bak
	sed "
	    s@<$pfo-x>..*</$pfo-x>@<$pfo-x>$1</$pfo-x>@;
	    s@<$pfo-y>..*</$pfo-y>@<$pfo-y>$2</$pfo-y>@;
	    /<name>/s@\[..*,..*\]@[$1,$2]@; #..*: for portability
	    " $aqx > $aqx.tmp
	mv $aqx.tmp $aqx
	set $aqx.bak $aqx
	ls -og $@
	#if which diff > /dev/null; then diff -U0 $@||:; fi
	;;
    aj) #shift AQX back to jidanni default X, Y
	if test $# -ne 1; then echo 1>&2 $0: Usage: $1; exit 86; fi
	exec sh $Z a 10 -5
	;;
    az) #shift AQX back to 0,0
	if test $# -ne 1; then echo 1>&2 $0: Usage: $1; exit 86; fi
	exec sh $Z a 0 0
	;;
esac