Server only accepts GK4 coordinates

[kiliankoe]

The server doesn't seem to be wanting to accept a coordinate converted from WGS84 to GK4 internally. Ugh.

curl -X "POST" "https://webapi.vvo-online.de/tr/pointfinder?format=json" \
     -H "Content-Type: application/json;charset=UTF-8" \
     -d $'{
  "limit": 0,
  "assignedstops": true,
  "query": "coord:5412867:5659752" # should be Albertplatz
}'

{
  "PointStatus": "NotIdentified",
  "Status": {
    "Code": "ServiceError",
    "Message": "no it connection"
  }
}

vs.

curl -X "POST" "https://webapi.vvo-online.de/tr/pointfinder?format=json" \
     -H "Content-Type: application/json;charset=UTF-8" \
     -d $'{
  "limit": 0,
  "assignedstops": true,
  "query": "coord:4621016:5655920" # should be Helmholtzstraße
}'

{
  "PointStatus": "Identified",
  "Status": {
    "Code": "Ok"
  },
  "Points": [
    "coord:4621020:504065:NAV4:Nöthnitzer Straße 46|c||Nöthnitzer Straße 46|5655935|4621020|0||",
    "33000742|||Helmholtzstraße|5655904|4621157|141||",
    "33000513|||Regensburger Straße|5655983|4620849|177||",
    "33000135|||Plauen Nöthnitzer Straße|5656060|4620527|507||",
    "33000134|||Münchner Platz|5656372|4620892|539||"
  ],
  "ExpirationTime": "\/Date(1488000580778+0100)\/"
}

[dirkonet]

coord:5412867:5659752

That's Gauss-Krüger zone 5. Convert it to zone 4 and it might be accepted. Dresden is in zone 5, but for some reason, all VVO coordinates are in zone 4 format.

[kiliankoe]

Dumping this here for posterity (so that I don't forget). Just checked with @lucasvog if it just comes down to a fixed offset, which it apparently does. We're not entirely sure about the exact values, but -789700 and 750 seem to work rather well.