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I use some similar like this one: Best practices when sending GPS location data

this for the encoder:
int32_t lat = latitude * 10000;
int32_t lon = longitude * 10000;
int16_t alt = altitudeGps * 100;
int8_t hdev = hdopGps * 10;

    if (ret == SUCCESS) {

        AppData[0] = lat;
        AppData[1] = lat >> 8;
        AppData[2] = lat >> 16;

        AppData[3] = lon;
        AppData[4] = lon >> 8;
        AppData[5] = lon >> 16;

        AppData[6] = alt;
        AppData[7] = alt >> 8;

        AppData[8] = hdev;

        AppDataSize = 9;

and this for the decoder:

function Decoder(b, port) {
var decoded = {};
switch (port) {
    case 2:
    var lat = (b[0] | b[1]<<8 | b[2]<<16 | (b[2] & 0x80 ? 0xFF<<24 : 0)) / 10000.0;
    var lon = (b[3] | b[4]<<8 | b[5]<<16 | (b[5] & 0x80 ? 0xFF<<24 : 0)) / 10000.0;
    var alt = (b[6] | b[7]<<8 | (b[7] & 0x80 ? 0xFFFF<<16 : 0)) / 100.0;
    var hdop = b[8] / 10.0;

        decoded = {
            "location": {
                "latitude": lat,
                "longitude": lon,
                "altitude": alt,
                "hdop": hdop
            },
        };
    break;

    case 3:
    var bat = (b[0] | b[1]<<8 | (b[1] & 0x80 ? 0xFFFF<<16 : 0)) * 10.0;

    decoded ={
        "battery":{
            "bat":bat
        }
    };
    break;

    case 4:
    var aX = (b[0] | b[1]<<8 | (b[1] & 0x80 ? 0xFFFF<<16 : 0)) / 10.0;
    var aY = (b[2] | b[3]<<8 | (b[3] & 0x80 ? 0xFFFF<<16 : 0)) / 10.0;
    var aZ = (b[4] | b[5]<<8 | (b[5] & 0x80 ? 0xFFFF<<16 : 0)) / 10.0;

    decoded ={
        "acceleration":{
            "aX":aX,
            "aY":aY,
            "aZ":aZ,
        }
    };
    break;
}
return decoded;

}

Tested in Salamanca (where I have negative longitude) and Budapest (all positive) and good results