Published
Edited
Sep 27, 2019
Importers
md`# GeoFx`
md`### Lookups`
geom_lu = ({
"point": {wkt: "POINT", json: "Point"},
"multipoint": {wkt: "MULTIPOINT", json: "MultiPoint"},
"linestring": {wkt: "LINESTRING", json: "LineString"},
"polygon": {wkt: "POLYGON", json: "Polygon"},
"multipolygon": {wkt: "MULTIPOLYGON", json: "MultiPolygon"},
})
md`### Transform`
function transform(x, y, epgs_from, epgs_to = epgs_lu[4326]) {
let format="ogcwkt"
let proj_from = epgs_lu[epgs_from]
let proj_to = epgs_lu[epgs_to]
return proj4(proj_from, proj_to, [x, y])
}
function transformArray(coordinates, epgs_from, epgs_to = epgs_lu[4326]) {
for(let i = 0; i < coordinates.length; i++) {
let point = coordinates[i]
coordinates[i] = transform(point[0], point[1], epgs_from, epgs_to)
}
return coordinates
}
function transformNestedArray(coordinates, epgs_from, epgs_to = epgs_lu[4326]) {
for(let i = 0; i < coordinates.length; i++) {
coordinates[i] = transformArray(coordinates[i], epgs_from, epgs_to)
/*
let coordinates = coordinates[i]
for(let j = 0; j < nested.length; j++) {
let point = nested[j]
nested[j] = transform(point[0], point[1], epgs_from, epgs_to)
}
coordinates[i] = nested
*/
}
return coordinates
}
function transformDoubleNestedArray(coordinates, epgs_from, epgs_to = epgs_lu[4326]) {
for(let i = 0; i < coordinates.length; i++) {
coordinates[i] = transformNestedArray(coordinates[i], epgs_from, epgs_to)
}
return coordinates
}
function transformFeature(geometry, epgs_from, epgs_to = epgs_lu[4326]) {
let type = geometry.type.toLowerCase()
let coordinates = geometry.coordinates
switch(type) {
case "point":
geometry.coordinates = transform(coordinates[0], coordinates[1], epgs_from, epgs_to)
break
case "linestring":
case "multipoint":
geometry.coordinates = transformArray(coordinates, epgs_from, epgs_to)
break;
case "polygon":
case "multilinestring":
geometry.coordinates = transformNestedArray(coordinates, epgs_from, epgs_to)
break;
case "multipolygon":
geometry.coordinates = transformDoubleNestedArray(coordinates, epgs_from, epgs_to)
break;
}
return geometry
}
md`### WKT to GeoJson`
function wktToJson(wkt) {
let type = wkt.split("(")[0]
let coords = wkt.replace(type, "")
type = type.replace(" ", "").toLowerCase()
coords = coords.split("(").join("[")
coords = coords.split(")").join("]")
coords = coords.split(", ").join("],[")
coords = coords.split(" ").join(",")
switch(type) {
case "multipoint":
coords = coords.split(']],[[').join('],[')
console.log(coords)
break
}
switch(type) {
case "multipolygon":
case "linestring":
coords = `[${coords}]`
break
}
type = geom_lu[type].json
coords = JSON.parse(coords)
return {
type: type,
coordinates: coords
}
}
wktToJson('MULTIPOINT ((4240098.5 879949.06), (4240375.5 878260), (4239721.5 878235.69))')
md`### GeoJson to WKT`
function jsonToWkt(json) {
let type = geom_lu[json.type.toLowerCase()].wkt
let coords = json.coordinates
coords = JSON.stringify(coords)
coords = coords.split(" ").join("")
coords = coords.split("[").join("(")
coords = coords.split("]").join(")")
coords = coords.split(",").join(" ")
coords = coords.split(") (").join(",")
// dirty fix - look into a cleaner fix
coords = coords.replace("((((", "(((")
coords = coords.replace("))))", ")))")
let wkt = `${type} ${coords}`
return wkt
}
md`### Function Examples`
JSON.stringify(wktToJson("MULTIPOLYGON (((40 40, 20 45, 45 30, 40 40)), ((20 35, 10 30, 10 10, 30 5, 45 20, 20 35), (30 20, 20 15, 20 25, 30 20)))"))
pt = wktToJson(`POINT (-123 44)`)
ln = wktToJson(`LINESTRING (30 10, 10 30, 40 40)`)
mp = wktToJson(`MULTIPOLYGON (((30 20, 45 40, 10 40, 30 20)),
((15 5, 40 10, 10 20, 5 10, 15 5)))`)
json = wktToJson(`MULTIPOLYGON (((4240798.8415422216 876707.41209763661, 4240938.0535376519 880733.89057715028, 4238928.0428281222 880796.74360999255, 4238508.9814029159 880807.24087823671, 4238440.4291313253 876762.80826649175, 4240798.8415422216 876707.41209763661)), ((4238788.55767483 875994.569164619, 4238790.99206148 875994.913981378, 4238793.33524065 875995.659061179, 4238795.52192354 875996.783078507, 4238797.49141452 875998.255193457, 4238799.18892348 876000.034067363, 4238800.56687818 876002.07015948, 4238801.58722083 876004.307367384, 4238802.22173616 876006.682698831, 4238802.45237954 876009.130865023, 4238802.27291735 876011.582968235, 4238803.14102881 876058.45803459, 4238805.57147844 876138.145811439, 4238807.51964393 876203.699710011, 4238810.11905706 876309.363901585, 4238797.28209662 876309.780896917, 4238647.83306617 876314.219879583, 4238645.93214485 876254.248994157, 4238642.12800561 876134.309847996, 4238641.49611494 876114.320974559, 4238638.30910257 876013.813942522, 4238638.21034914 876000.47173202, 4238689.77308618 875998.562280506, 4238788.55767483 875994.569164619)))`)
json2 = transformFeature(json, 2914, 4326)
transformFeature(point, 4326, 2914)
point = ({
"type": "Point",
"coordinates": [-123, 44]
})
transformFeature(multiPoint, 4326, 2914)
multiPoint = ({
"type": "MultiPoint",
"coordinates": [
[-123, 43], [-123, 44], [-123, 45], [-135, 45]
]
})
transformFeature(lineString, 4326, 2914)
lineString = ({
"type": "LineString",
"coordinates": [
[-123, 43], [-123, 44], [-123, 45], [-135, 45]
]
})
transformFeature(multiLineString, 4326, 2914)
multiLineString = ({
"type": "MultiLineString",
"coordinates": [
[[-123, 43], [-123, 44], [-123, 45], [-135, 45]],
[[-124, 43], [-124, 42], [-125, 44], [-135, 41]]
]
})
transformFeature(polygon, 4326, 2914)
polygon = ({
"type": "Polygon",
"coordinates": [
[
[-120.0, 44.0], [-121.0, 44.0], [-121.0, 45.0],
[-120.0, 45.0], [-120.0, 44.0]
]
]
})
transformFeature(multiPolygon, 4326, 2914)
multiPolygon = ({
"type": "MultiPolygon",
"coordinates": [
[
[[40, 40], [20, 45], [45, 30], [40, 40]]
],
[
[[20, 35], [10, 30], [10, 10], [30, 5], [45, 20], [20, 35]],
[[30, 20], [20, 15], [20, 25], [30, 20]]
]
]
})
eug_json.features[0].geometry
transformFeature(eug_json.features[0].geometry, 4326, 2914)
eug_json = fetch("https://gl.githack.com/epdcau/observable/raw/master/data/geojson/city_limits.geojson")
.then( data => data.json() )
.then( ( data ) => {
data.features = data.features.filter( f => f.properties.inccityabb == "EUG" );
return data;
})
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md`### Libraries`
proj4 = require('proj4@2')
md`### To Purge`
async function epgs(epgs) {
let format="ogcwkt"
let epgs_url = `https://raw.githubusercontent.com/GeographicDesign/projections/master/epsg/${epgs}/${format}.txt`
return await fetch(epgs_url)
.then(d => d.text())
}
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