CODEWITHSUNDEEP
pythonmatplotlib-basemap
jonplaca
jonplaca

Reputation: 827

Basemap - Values must be between -90, 90 Degrees

OBJECTIVE

APPROACH

Using this tutorial on Basemap, upload a shapefile for mapping.

#First, we have to import our datasets. 
#These datasets include store locations, existing distribution locations, county borders, and real estate by county
walmartStores = pd.read_csv("data/walmart-stores.csv",header=0, encoding='latin1')
propertyValues = pd.read_csv("data/property values.csv")
shp = fiona.open('data/boundaries/Counties.shp')


#We need to create a workable array with Walmart Stores
longitude = walmartStores.longitude
latitude = walmartStores.latitude
stores = np.column_stack((longitude, latitude))

#We also need to load the shape file for county boundaries
extra = 0.1 
bds = shp.bounds 
shp.close()

#We need to assign the lower-left bound and upper-right bound
ll = (bds[0], bds[1])
ur = (bds[2], bds[3])


#concatenate the lower left and upper right into a variable called coordinates
coords = list(chain(ll, ur))
print(coords)

#define variables for the width and the height of the map
w, h = coords[2] - coords[0], coords[3] - coords[1]

with print(coords) = [105571.4206781257, 4480951.235680977, 779932.0626624253, 4985476.422250552]

All is well thus far, however I run into a problem below:

m = Basemap(
    #set projection to 'tmerc' to minimize map distortion
    projection='tmerc',

    #set longitude as average of lower, upper longitude bounds
    lon_0 = np.average([bds[0],bds[2]]),

    #set latitude as average of lower,upper latitude bounds
    lat_0 = np.average([bds[1],bds[3]]),

    #string describing ellipsoid (‘GRS80’ or ‘WGS84’, for example). 
    #Not sure what this does...
    ellps = 'WGS84',

    #set the map boundaries. Note that we use the extra variable to provide a 10% buffer around the map
    llcrnrlon=coords[0] - extra * w,
    llcrnrlat=coords[1] - extra + 0.01 * h,
    urcrnrlon=coords[2] + extra * w,
    urcrnrlat=coords[3] + extra + 0.01 * h,

    #provide latitude of 'true scale.' 
    #check the Basemap API
    lat_ts=0,

    #resolution of boundary database to use. Can be c (crude), l (low), i (intermediate), h (high), f (full) or None.
    resolution='i',

    #don't show the axis ticks automatically
    suppress_ticks = False)


m.readshapefile(
    #provide the path to the shapefile, but leave off the .shp extension
    'data/boundaries/Counties.shp',

    #name your map something useful (I named this 'srilanka')
    'nyCounties',

    #set the default shape boundary coloring (default is black) and the zorder (layer order)
    color='none',
    zorder=2)

Error: lat_0 must be between -90.000000 and 90.000000

QUESTIONS

  1. lat_0 and lon_0 aren't between -90 and 90. However, lon_0 doesn't throw an error. Why is this the case?
  2. I've looked online for others facing a similar issue and have come up empty handed. Is there something unique with my notebook? (NOTE: conda list shows `basemap 1.0.7, so I know that it's installed and running)

Thanks!

Upvotes: 2

Views: 457

Answers (1)

Ken Syme
Ken Syme

Reputation: 3632

Latitude can only be between -90 and 90 - anything else doesn't makes sense. The North pole is +90 and the South pole is -90, with the equator at 0. There are no other acceptable values!

Regarding longtitude, it can only be between -180 and 180. 0 is at the Prime Meridian and going to -180 (westward) and +180 (eastward)

Upvotes: 0

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