How to Retrieve Images from HERE API Preserving Geometry: A Comprehensive Guide

Are you struggling to retrieve images from the HERE API while preserving their geometry? Look no further! In this article, we’ll take you on a step-by-step journey to master the art of image retrieval from the HERE API, ensuring that the resulting images retain their original geometry.

What is the HERE API?

The HERE API is a powerful tool provided by HERE Technologies, a leader in location-based services. It offers a wide range of APIs and SDKs that enable developers to build innovative location-based applications. One of the key features of the HERE API is its ability to provide high-quality map images, which can be customized to meet specific requirements.

Why Preserve Geometry?

When retrieving images from the HERE API, it’s essential to preserve their geometry to maintain the accuracy and usefulness of the images. Geometry refers to the spatial relationships between objects within the image, including the position, scale, and orientation of features such as buildings, roads, and other map elements. Preserving geometry ensures that the resulting images are not distorted, stretched, or skewed, which can lead to incorrect interpretations and decisions.

Challenges in Preserving Geometry

Retrieving images from the HERE API while preserving their geometry can be challenging due to several factors:

• Coordinate Systems: The HERE API uses a specific coordinate system, which may differ from the one used in your application. Ensuring that the coordinate systems are properly aligned is crucial to preserving geometry.
• Image Projections: Images from the HERE API can be projected in various ways, affecting their geometry. Understanding the projection methods and their implications is vital to preserving geometry.
• Image Scales and Resolutions: The scale and resolution of the retrieved images can impact their geometry. Choosing the correct scale and resolution is essential to preserving the original geometry.

Step-by-Step Guide to Retrieving Images from HERE API Preserving Geometry

Now that we’ve discussed the importance of preserving geometry, let’s dive into the step-by-step process of retrieving images from the HERE API while maintaining their original geometry.

Step 1: Set Up Your HERE API Account and Project

Before you can start retrieving images, you need to set up your HERE API account and create a new project. Follow these steps:

1. Go to the HERE Developer Portal and create an account if you haven’t already.
2. Click on the “Create a new project” button and fill in the required information.
3. Choose the “Maps” API and select the “Raster Tiles” option.
4. Click on the “Create project” button to create your new project.

Step 2: Understand the HERE API Image Retrieval Endpoints

The HERE API provides several endpoints for retrieving images. For preserving geometry, we’ll focus on the following endpoints:

• https://api.here.com/2/maptile/2.1/maptile/newest/{z}/{x}/{y}/256/png8 – Retrieves a map tile image with a specific zoom level (z), x-coordinate, and y-coordinate.
• https://api.here.com/2/maptile/2.1/maptile/newest/{z}/{x}/{y}/256/png8?app_id={appid}&app_code={appcode} – Retrieves a map tile image with authentication using app_id and app_code.

Step 3: Choose the Correct Coordinate System and Projection

To preserve geometry, it’s essential to use the correct coordinate system and projection. The HERE API uses the Web Mercator projection (EPSG:3857) by default. If your application uses a different coordinate system, you’ll need to transform the coordinates accordingly.

// Example of transforming coordinates from WGS84 ( EPSG:4326 ) to Web Mercator ( EPSG:3857 )
function transformCoordinates(lat, lon) {
  const x = lon * 20037508.34 / 180;
  const y = Math.log(Math.tan((90 + lat) * Math.PI / 180)) * 20037508.34 / Math.PI;
  return { x, y };
}

Step 4: Set the Correct Image Scale and Resolution

The scale and resolution of the retrieved images impact their geometry. To preserve geometry, use the following guidelines:

Zoom Level (z)	Scale	Resolution (px)
0-5	1:35,877,408	256×256
6-10	1:17,938,704	512×512
11-15	1:8,969,352	1024×1024

Step 5: Construct the HERE API Request and Authenticate

Now that you’ve chosen the correct coordinate system, projection, scale, and resolution, it’s time to construct the HERE API request.

// Example of constructing the HERE API request
function getMapTile(z, x, y) {
  const apiUrl = `https://api.here.com/2/maptile/2.1/maptile/newest/${z}/${x}/${y}/256/png8`;
  const appId = "YOUR_APP_ID";
  const appCode = "YOUR_APP_CODE";
  const authService = `app_id=${appId}&app_code=${appCode}`;
  const requestUrl = `${apiUrl}?${authService}`;
  return requestUrl;
}

Step 6: Retrieve and Display the Image

Use the constructed request URL to retrieve the map tile image and display it in your application.

// Example of retrieving and displaying the image
function displayMapTile(z, x, y) {
  const requestUrl = getMapTile(z, x, y);
  const img = document.createElement("img");
  img.src = requestUrl;
  document.body.appendChild(img);
}

Best Practices for Preserving Geometry

To ensure that your retrieved images preserve their geometry, follow these best practices:

• Use the Correct Coordinate System: Ensure that your application uses the same coordinate system as the HERE API (Web Mercator, EPSG:3857) or transform the coordinates accordingly.
• Choose the Correct Scale and Resolution: Select the appropriate scale and resolution for your application to maintain the original geometry of the images.
• Use the Right Projection: The HERE API uses the Web Mercator projection by default. If your application requires a different projection, ensure that you transform the coordinates correctly.
• Authenticate Your Requests: Always authenticate your requests using your app_id and app_code to ensure that your requests are valid and geometry-preserving.

Conclusion

In this comprehensive guide, we’ve covered the steps to retrieve images from the HERE API while preserving their geometry. By following these steps and best practices, you can ensure that your retrieved images maintain their original geometry, providing accurate and reliable information for your users. Happy coding!

Frequently Asked Question

Here are some frequently asked questions about how to retrieve images from HERE API while preserving geometry.