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# -*- coding: utf-8 -*- 

 

u'''Functions to obtain elevations and geoid heights thru web services, 

for (lat, lon) locations, currently limited to the U{Conterminous US 

(CONUS)<https://WikiPedia.org/wiki/Contiguous_United_States>}, see also 

module L{geoids}, module L{heights} classes and U{USGS10mElev.py 

<https://Gist.GitHub.com/pyRobShrk>}. 

 

B{macOS}: If an C{SSLCertVerificationError} occurs, especially this 

I{"[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: self 

"signed certificate in certificate chain ..."}, review U{this post 

<https://StackOverflow.com/questions/27835619/urllib-and-ssl-certificate 

-verify-failed-error>} for a remedy. From a Terminal window run: 

C{"/Applications/Python X.Y/Install Certificates.command"} 

 

@newfield example: Example, Examples 

''' 

 

from pygeodesy.fmath import fStr 

from pygeodesy.lazily import _ALL_LAZY 

from pygeodesy.named import Elevation2Tuple, GeoidHeight2Tuple 

from pygeodesy.utily import clipStr 

 

__all__ = _ALL_LAZY.elevations 

__version__ = '20.02.07' 

 

try: 

_Bytes = unicode, bytearray # PYCHOK expected 

from urllib2 import urlopen # quote, urlcleanup 

from httplib import HTTPException as HTTPError 

 

except (ImportError, NameError): # Python 3+ 

_Bytes = bytes, bytearray 

from urllib.request import urlopen # urlcleanup 

# from urllib.parse import quote 

from urllib.error import HTTPError 

 

try: 

from json import loads as _json 

except ImportError: 

 

def _json(ngs): # PYCHOK no cover 

'''(INTERNAL) Convert an NGS response in JSON to a C{dict}. 

''' 

# b'{"geoidModel": "GEOID12A", 

# "station": "UserStation", 

# "lat": 37.8816, 

# "latDms": "N375253.76000", 

# "lon": -121.9142, 

# "lonDms": "W1215451.12000", 

# "geoidHeight": -31.703, 

# "error": 0.064 

# }' 

# 

# or in case of errors: 

# 

# b'{"error": "No suitable Geoid model found for model 15" 

# }' 

d = {} 

for t in ngs.strip().lstrip('{').rstrip('}').split(','): 

j = t.strip().strip('"').split('": ') 

if len(j) != 2: 

raise ValueError('json: %r' % (t,)) 

k, v = j 

try: 

v = float(v) 

except ValueError: 

v = v.lstrip().lstrip('"') 

d[k] = v 

return d 

 

 

def _error(fun, lat, lon, e): 

'''(INTERNAL) Format an error 

''' 

return '%s(%s): %s' % (fun.__name__, fStr((lat, lon)), e) 

 

 

def _qURL(url, params, timeout=2): 

'''(INTERNAL) Build B{C{url}} query, get and verify response. 

''' 

if params: # build url query, do not map(quote, params)! 

url += '?' + '&'.join(_ for _ in map(str, params) if _) 

u = urlopen(url, timeout=timeout) # secs 

 

s = u.getcode() 

if s != 200: # http.HTTPStatus.OK or http.client.OK 

raise IOError('code %d: %s' % (s, u.geturl())) 

 

r = u.read() 

u.close() 

# urlcleanup() 

return _str(r).strip() 

 

 

def _str(t): 

'''Unicode or C{bytes} to C{str}. 

''' 

if isinstance(t, _Bytes): 

t = str(t.decode('utf-8')) 

return t 

 

 

def _xml(tag, xml): 

'''(INTERNAL) Get a <tag>value</tag> from XML. 

''' 

# b'<?xml version="1.0" encoding="utf-8" ?> 

# <USGS_Elevation_Point_Query_Service> 

# <Elevation_Query x="-121.914200" y="37.881600"> 

# <Data_Source>3DEP 1/3 arc-second</Data_Source> 

# <Elevation>3851.03</Elevation> 

# <Units>Feet</Units> 

# </Elevation_Query> 

# </USGS_Elevation_Point_Query_Service>' 

i = xml.find('<%s>' % (tag,)) 

if i > 0: 

i += len(tag) + 2 

j = xml.find('</%s>' % (tag,), i) 

if j > i: 

return xml[i:j].strip() 

return 'no XML tag <%s>' % (tag,) 

 

 

def elevation2(lat, lon, timeout=2.0): 

'''Get the geoid elevation at an C{NAD83} to C{NAVD88} location. 

 

@param lat: Latitude (C{degrees}). 

@param lon: Longitude (C{degrees}). 

@keyword timeout: Optional, query timeout (seconds). 

 

@return: An L{Elevation2Tuple}C{(elevation, data_source)} 

or (C{None, "error"}) in case of errors. 

 

@note: The returned C{elevation} is C{None} if B{C{lat}} or B{C{lon}} 

is invalid or outside the C{Conterminous US (CONUS)}, 

if conversion failed or if the query timed out. The 

C{error} is the C{HTTP-, IO-, SSL-, Type-, URL-} or 

C{ValueError} as a string (C{str}). 

 

@see: U{USGS National Map<https://NationalMap.gov/epqs>}, 

the U{FAQ<https://www.USGS.gov/faqs/what-are-projection- 

horizontal-and-vertical-datum-units-and-resolution-3dep-standard-dems>}, 

U{geoid.py<https://Gist.GitHub.com/pyRobShrk>}, module 

L{geoids}, classes L{GeoidG2012B}, L{GeoidKarney} and 

L{GeoidPGM}. 

''' 

try: 

x = _qURL('https://NED.USGS.gov/epqs/pqs.php', # https://NationalMap.gov/epqs/pqs.php 

('x=%.6f' % (lon,), 

'y=%.6f' % (lat,), 

'units=Meters', # Feet 

'output=xml'), 

timeout=float(timeout)) 

if x[:6] == '<?xml ': 

e = _xml('Elevation', x) 

try: 

e = float(e) 

if -1000000 < e < 1000000: 

return Elevation2Tuple(e, _xml('Data_Source', x)) 

e = 'non-CONUS %.2f' % (e,) 

except ValueError: 

pass 

else: 

e = 'no XML "%s"' % (clipStr(x, limit=128, white=' '),) 

except (HTTPError, IOError, TypeError, ValueError) as x: 

e = repr(x) 

return Elevation2Tuple(None, _error(elevation2, lat, lon, e)) 

 

 

def geoidHeight2(lat, lon, model=0, timeout=2.0): 

'''Get the C{NAVD88} geoid height at an C{NAD83} location. 

 

@param lat: Latitude (C{degrees}). 

@param lon: Longitude (C{degrees}). 

@keyword model: Optional, geoid model ID (C{int}). 

@keyword timeout: Optional, query timeout (seconds). 

 

@return: An L{GeoidHeight2Tuple}C{(height, model_name)} 

or C{(None, "error"}) in case of errors. 

 

@note: The returned C{height} is C{None} if B{C{lat}} or B{C{lon}} is 

invalid or outside the C{Conterminous US (CONUS)}, if the 

B{C{model}} was invalid, if conversion failed or if the 

query timed out. The C{error} is the C{HTTP-, IO-, SSL-, 

Type-, URL-} or C{ValueError} as a string (C{str}). 

 

@see: U{NOAA National Geodetic Survey 

<https://www.NGS.NOAA.gov/INFO/geodesy.shtml>}, 

U{Geoid<https://www.NGS.NOAA.gov/web_services/geoid.shtml>}, 

U{USGS10mElev.py<https://Gist.GitHub.com/pyRobShrk>}, module 

L{geoids}, classes L{GeoidG2012B}, L{GeoidKarney} and 

L{GeoidPGM}. 

''' 

try: 

j = _qURL('https://Geodesy.NOAA.gov/api/geoid/ght', 

('lat=%.6f' % (lat,), 

'lon=%.6f' % (lon,), 

'model=%s' % (model,) if model else ''), 

timeout=float(timeout)) # PYCHOK 5 

if j[:1] == '{' and j[-1:] == '}' and j.find('"error":') > 0: 

d = _json(j) 

if isinstance(d.get('error', 'N/A'), float): 

h = d.get('geoidHeight', None) 

if h is not None: 

m = _str(d.get('geoidModel', 'N/A')) 

return GeoidHeight2Tuple(h, m) 

e = 'geoidHeight' 

else: 

e = 'JSON' 

e = 'no %s "%s"' % (e, clipStr(j, limit=256, white=' ')) 

except (HTTPError, IOError, TypeError, ValueError) as x: 

e = repr(x) 

e = _error(geoidHeight2, lat, lon, e) 

return GeoidHeight2Tuple(None, e) 

 

 

if __name__ == '__main__': 

 

# <https://WikiPedia.org/wiki/Mount_Diablo> 

for f in (elevation2, # (1173.79, '3DEP 1/3 arc-second') 

geoidHeight2): # (-31.703, 'GEOID12B') 

t = f(37.8816, -121.9142) 

print('%s: %s' % (f.__name__, t)) 

 

# **) MIT License 

# 

# Copyright (C) 2016-2020 -- mrJean1 at Gmail -- All Rights Reserved. 

# 

# Permission is hereby granted, free of charge, to any person obtaining a 

# copy of this software and associated documentation files (the "Software"), 

# to deal in the Software without restriction, including without limitation 

# the rights to use, copy, modify, merge, publish, distribute, sublicense, 

# and/or sell copies of the Software, and to permit persons to whom the 

# Software is furnished to do so, subject to the following conditions: 

# 

# The above copyright notice and this permission notice shall be included 

# in all copies or substantial portions of the Software. 

# 

# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS 

# OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 

# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 

# THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR 

# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 

# ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR 

# OTHER DEALINGS IN THE SOFTWARE. 

 

# % python -m pygeodesy.elevations 

# elevation2: (1173.79, '3DEP 1/3 arc-second') 

# geoidHeight2: (-31.703, 'GEOID12B')