I have tried to use javascript to perform the action but am running in to issues with the returned json. I am connected through an Enterprise account but if I use the parent url the below script returns the error 'Token Required'. The error in Survey123 is always the same. I can use a child layer and paste the identify url in a browser but it will only return the layer attributes, never the value of the coordinates.
// rasterPixelValue.js
// Call from XLSForm: pulldata("@javascript", "rasterPixelValue.js", "getRasterValue", imageServiceUrl, longitude, latitude)
function getRasterValue(imageServiceUrl, longitude, latitude) {
// Validate inputs
if (!imageServiceUrl || !longitude || !latitude) {
return "Error: Missing required parameters (imageServiceUrl, longitude, latitude)";
}
// Convert coordinates to numbers
const lon = parseFloat(longitude);
const lat = parseFloat(latitude);
if (isNaN(lon) || isNaN(lat)) {
return "Error: Invalid coordinates";
}
try {
// Build the identify request URL
const identifyUrl = imageServiceUrl.endsWith('/')
? imageServiceUrl + 'identify'
: imageServiceUrl + '/identify';
// Create the geometry parameter
const geometry = JSON.stringify({
x: lon,
y: lat,
spatialReference: { wkid: 4326 }
});
// Build request parameters manually
const params = [
'geometry=' + encodeURIComponent(geometry),
'geometryType=esriGeometryPoint',
'returnGeometry=false',
'returnCatalogItems=false',
'f=json'
];
const requestUrl = identifyUrl + '?' + params.join('&');
// Make synchronous request (required for Survey123 pulldata functions)
const xhr = new XMLHttpRequest();
xhr.open('GET', requestUrl, false); // false = synchronous
xhr.withCredentials = true;
xhr.send();
if (xhr.status === 200) {
const response = JSON.parse(xhr.responseText);
// Check for errors in response
if (response.error) {
return "Error: " + response.error.message + " " +requestUrl;
}
// Extract pixel value
let pixelValue = null;
if (response.value !== undefined && response.value !== null) {
pixelValue = response.value;
} else if (response.values && response.values.length > 0) {
// For multi-band rasters, return first band or comma-separated values
pixelValue = response.values.length === 1 ? response.values[0] : response.values.join(',');
} else if (response.properties && Object.keys(response.properties).length > 0) {
// Sometimes pixel data is in properties
const keys = Object.keys(response.properties);
pixelValue = response.properties[keys[0]]; // Return first property value
}
// Return the pixel value or "No Data" if null/undefined
return pixelValue !== null && pixelValue !== undefined ? pixelValue.toString() : "No Data";
} else {
return "Error: HTTP " + xhr.status + " - Unable to query image service";
}
} catch (error) {
return "Error: " + error.message;
}
}
