01 Downloading OSM File.md

Readme

This script downloads an OSM file and saves it to drive from a centre point or a search term

Input Varaiable

• search - [string] Search query of the location
• midLat - [float] (optional) latitude of the building
• midLon - [float] (optional) longitude of the building
• bbox - [int] Dimension of one side of bounding box for OSM
• path - [string] A folder directory to save the OSM File
• run - [boolean] A boolean toggle to download the OSM file (Run once)

01 Load Libraries

import xml.etree.ElementTree as ET
import ghpythonlib.treehelpers as th
import math
import urllib2
import json

02 Generate an API Key from positionstack

www.positionstack.com

KEY = 'YOUR API KEY HERE'

Create option to either search or use manual midLat and midLon

if search:
    print 'Search Tag found' 
    query = search.replace(" ", "%20")
    url = 'http://api.positionstack.com/v1/forward?access_key='+KEY+'&query='+query
    response = urllib2.urlopen(url)
    data = json.load(response)   
    midLon = data['data'][0]['longitude']
    midLat = data['data'][0]['latitude']
else:
    print 'Search Tag not Found. Enter search term or use midLat and midLon'

Constants for calculating the bounding box

R = 6371000

03 Bounding Box calculation

#111110 is the distance of 1 degree in meters for the Y direction (Latitude) #X distance per degree = [cosine(latitude)*Y distance in radians] #bbox here is the dimension of the boundarybox side

dY = (bbox/2) / 111110
dX = dY / math.cos(math.radians(midLat))

Calculation the extents of the bounding box

a = str(midLon - dX)
b = str(midLat - dY)
c = str(midLon + dX)
d = str(midLat + dY)
bbox = a +','+ b + ',' + c + ',' + d

04 Requesting OSM file from OverpassAPI

url = 'https://overpass-api.de/api/map?bbox='+bbox
if run:
    response = urllib2.urlopen(url)
    filePath = path+'file.osm'
    mydata = response.read()
    file = open(filePath, "w")
    file.write(mydata)
    file.close()
else:
    filePath = path+'file.osm'