def geteastingshift(self, zonen: float, zonel: float) -> Optional[float]:
"""
If the lat, lon coordinates being converted are located in a
different UTM zone than the canvas reference point, the UTM meters
may need to be shifted.
This picks a reference point in the same longitudinal band
(UTM zone number) as the provided zone, to calculate the shift in
meters for the x coordinate.
:param zonen: zonen
:param zonel: zone1
:return: the x shift value
"""
rzonen = int(self.refutm[0][0])
# same zone number, no x shift required
if zonen == rzonen:
return None
z = (zonen, zonel)
# x shift already calculated, cached
if z in self.zoneshifts and self.zoneshifts[z][0] is not None:
return self.zoneshifts[z][0]
rlat, rlon, _ralt = self.refgeo
# ea. zone is 6deg band
lon2 = rlon + 6 * (zonen - rzonen)
# ignore northing
e2, _n2, _zonen2, _zonel2 = utm.from_latlon(rlat, lon2)
# NOTE: great circle distance used here, not reference ellipsoid!
xshift = utm.haversine(rlon, rlat, lon2, rlat) - e2
# cache the return value
yshift = None
if z in self.zoneshifts:
yshift = self.zoneshifts[z][1]
self.zoneshifts[z] = (xshift, yshift)
return xshift
def getutmzoneshift(
self, e: float, n: float
) -> Tuple[float, float, Tuple[float, str]]:
"""
Given UTM easting and northing values, check if they fall outside
the reference point's zone boundary. Return the UTM coordinates in a
different zone and the new zone if they do. Zone lettering is only
changed when the reference point is in the opposite hemisphere.
:param e: easting value
:param n: northing value
:return: modified easting, northing, and zone values
"""
zone = self.refutm[0]
rlat, rlon, _ralt = self.refgeo
if e > 834000 or e < 166000:
num_zones = (int(e) - 166000) / (utm.R / 10)
# estimate number of zones to shift, E (positive) or W (negative)
rlon2 = self.refgeo[1] + (num_zones * 6)
_e2, _n2, zonen2, zonel2 = utm.from_latlon(rlat, rlon2)
xshift = utm.haversine(rlon, rlat, rlon2, rlat)
# after >3 zones away from refpt, the above estimate won't work
# (the above estimate could be improved)
if not 100000 <= (e - xshift) < 1000000:
# move one more zone away
num_zones = (abs(num_zones) + 1) * (abs(num_zones) / num_zones)
rlon2 = self.refgeo[1] + (num_zones * 6)
_e2, _n2, zonen2, zonel2 = utm.from_latlon(rlat, rlon2)
xshift = utm.haversine(rlon, rlat, rlon2, rlat)
e = e - xshift
zone = (zonen2, zonel2)
if n < 0:
# refpt in northern hemisphere and we crossed south of equator
n += 10000000
zone = (zone[0], "M")
elif n > 10000000:
# refpt in southern hemisphere and we crossed north of equator
n -= 10000000
zone = (zone[0], "N")
return e, n, zone
def getnorthingshift(self, zonen: float, zonel: float) -> Optional[float]:
"""
If the lat, lon coordinates being converted are located in a
different UTM zone than the canvas reference point, the UTM meters
may need to be shifted.
This picks a reference point in the same latitude band (UTM zone letter)
as the provided zone, to calculate the shift in meters for the
y coordinate.
:param zonen: zonen
:param zonel: zone1
:return: calculated y shift
"""
rzonel = self.refutm[0][1]
# same zone letter, no y shift required
if zonel == rzonel:
return None
z = (zonen, zonel)
# y shift already calculated, cached
if z in self.zoneshifts and self.zoneshifts[z][1] is not None:
return self.zoneshifts[z][1]
rlat, rlon, _ralt = self.refgeo
# zonemap is used to calculate degrees difference between zone letters
latshift = self.zonemap[zonel] - self.zonemap[rzonel]
# ea. latitude band is 8deg high
lat2 = rlat + latshift
_e2, n2, _zonen2, _zonel2 = utm.from_latlon(lat2, rlon)
# NOTE: great circle distance used here, not reference ellipsoid
yshift = -(utm.haversine(rlon, rlat, rlon, lat2) + n2)
# cache the return value
xshift = None
if z in self.zoneshifts:
xshift = self.zoneshifts[z][0]
self.zoneshifts[z] = (xshift, yshift)
return yshift
