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script for turning esri json into geojson
function toGeoJSON(data){
var outPut = { "type": "FeatureCollection",
"features": []};
var fl = data.features.length;
var i = 0;
while(fl>i){
var ft = data.features[i];
/* as only ESRI based products care if all the features are the same type of geometry, check for geometry type at a feature level*/
var outFT = {
"type": "Feature",
"properties":ft.attributes
};
if(ft.geometry.x){
//check if it's a point
outFT.geometry=point(ft.geometry);
}else if(ft.geometry.points){
//check if it is a multipoint
outFT.geometry=points(ft.geometry);
}else if(ft.geometry.paths){
//check if a line (or "ARC" in ESRI terms)
outFT.geometry=line(ft.geometry);
}else if(ft.geometry.rings){
//check if a poly.
outFT.geometry=poly(ft.geometry);
}
outPut.features.push(outFT);
i++;
}
function point(geometry){
//this one is easy
return {"type": "Point","coordinates": [geometry.x,geometry.y]};
}
function points(geometry){
//checks if the multipoint only has one point, if so exports as point instead
if(geometry.points.length===1){
return {"type": "Point","coordinates": geometry.points[0]};
}else{
return { "type": "MultiPoint","coordinates":geometry.points};
}
}
function line(geometry){
//checks if their are multiple paths or just one
if(geometry.paths.length===1){
return {"type": "LineString","coordinates": geometry.paths[0]};
}else{
return { "type": "MultiLineString","coordinates":geometry.paths};
}
}
function poly(geometry){
//first we check for some easy cases, like if their is only one ring
if(geometry.rings.length===1){
return {"type": "Polygon","coordinates": geometry.rings};
}else{
/*if it isn't that easy then we have to start checking ring direction, basically the ring goes clockwise its part of the polygon, if it goes counterclockwise it is a hole in the polygon, but geojson does it by haveing an array with the first element be the polygons and the next elements being holes in it*/
var ccc= dP(geometry.rings);
var d = ccc[0];
var dd = ccc[1];
var r=[];
if(dd.length===0){
/*if their are no holes we don't need to worry about this, but do need to stuck each ring inside its own array*/
var l2 = d.length;
var i3 = 0;
while(l2>i3){
r.push([d[i3]]);
}
return { "type": "MultiPolygon","coordinates":r};
}else if(d.length===1){
/*if their is only one clockwise ring then we know all holes are in that poly*/
dd.unshift(d[0]);
return {"type": "Polygon","coordinates": dd};
}else{
/*if their are multiple rings and holes we have no way of knowing which belong to which without looking at it specially, so just dump the coordinates and add a hole field, this may cause errors*/
return { "type": "MultiPolygon","coordinates":d, "holes":dd};
}
}
}
function dP(a){
//returns an array of 2 arrays, the first being all the clockwise ones, the second counter clockwise
var d = [];
var dd =[];
var l = a.length;
var ii = 0;
while(l>ii){
if(c(a[ii])){
d.push(a[ii]);
}else{
dd.push(a[ii]);
}
ii++;
}
return [d,dd];
}
function c(a){
//return true if clockwise
var l = a.length-1;
var i = 0;
var o=0;
while(l>i){
o+=(a[i][0]*a[i+1][1]-a[i+1][0]*a[i][1]);
i++;
}
return o<=0;
}
return outPut;
}
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