Converst gpx to Inkscape sag

gpx-to-svg.py

#!/usr/bin/env python3

# eg 50.84,4.35 is a gps coordinate in brussels . vw/vh is the amount of degrees. eg 0.06 => around 6km. It is the left lower corner as in the north space degrees go up if you move north (but in svg it is the other way around)
# ./loopgpx.py  -vy 50.84 -vx 4.35 -vw 0.06 -vh 0.06 -width 1000 -height 1000 "file1.gpx" "file2.gpx" "file3.gpx" > map-of-multiple-loops.svg

# it uses print instead of propper xml tree building cause well hmm, i'm lazy and this should work as well if you don't use exotic file names

import sys
import argparse
import xml.etree.ElementTree as ET
import math

parser = argparse.ArgumentParser()
parser.add_argument("gpx",nargs='+')
parser.add_argument("-height",type=float)
parser.add_argument("-width",type=float)

parser.add_argument("-vx",type=float)
parser.add_argument("-vy",type=float)

parser.add_argument("-vw",type=float)
parser.add_argument("-vh",type=float)


args = parser.parse_args()

# i saw this formula on multiple websites, it seems to give a good approximation for the ratio
r = math.cos(args.vy*math.pi/180)

viewbox = "{} {} {} {}".format(0,0,args.vw,args.vh)

paths = []

for g in args.gpx:
  tree = ET.parse(g)
  root = tree.getroot()

  xmlns = "http://www.topografix.com/GPX/1/1"

  q = ".//{{{}}}{}".format(xmlns,"trkpt")


  listp = []

  pathtag = "M"
  for ptx in root.findall(q):
    #lon is the x axis
    #lat is reverse y axis

    lat = -(float(ptx.attrib["lat"]))+args.vy+args.vh
    lon = (float(ptx.attrib["lon"])-args.vx)*r
    
    listp.append("{} {},{}".format(pathtag,lon,lat))
    pathtag = "L"
  
  paths.append("<path inkscape:label=\"{}\"  d=\"{}\"/>".format(g," ".join(listp)))


print("<svg viewBox=\"{}\" width=\"{}\" height=\"{}\"><g id=\"gpxmap\" inkscape:label=\"gpxmap\">{}</g><g id=\"info\"><text style=\"font: {}px\">{}</text></g></svg>".format(viewbox,args.width,args.height," ".join(paths),args.vh/5," ".join(sys.argv)))