double y1 = din.readDouble();
double y2 = din.readDouble();
if (h.flags.getEnvelopeIndicator().value > 1) {
// 2 = minz,maxz; 3 = minm,maxm - we ignore these for now
din.readDouble();
din.readDouble();
}
if (h.flags.getEnvelopeIndicator().value > 3) {
// 4 = minz,maxz,minm,maxm - we ignore these for now