ER Mapper 7.0 tutorial part 4 (cell coordinates)

Summary

This video script provides a step-by-step guide on how to measure pixel locations and distances within an image using a mapping or GIS software. It explains how to view pixel coordinates and real-world locations (longitude/latitude) by selecting points within the image. Additionally, it covers the process of measuring distances in different units, including imperial and metric units, as well as cell coordinates. Users can also manually measure pixel distances by selecting specific pixels in the image. This functionality is useful for accurately identifying locations and distances within digital images.

Takeaways

• 😀 You can view pixel coordinates by selecting 'Cell Coordinates' under the 'View' menu or by right-clicking on the image.
• 😀 The location of any selected pixel in the image is given by its x and y coordinates (e.g., 1.1 for both x and y for the first pixel).
• 😀 The pixel coordinates are referenced within the image’s grid, which for this example is a 500x500 pixel image.
• 😀 You can also view real-world geographic coordinates (longitude and latitude) for the selected pixel based on the geographic coordinate system.
• 😀 The software supports displaying distances in different units, including imperial, feet, and metric (kilometers and meters).
• 😀 You can measure distances within the image by selecting two points and dragging the pointer to calculate the distance between them.
• 😀 For example, the distance between two points might be 0.30 miles in imperial units or 492.10 meters in metric units.
• 😀 The software also displays the number of pixels between two selected points, which corresponds to the image’s original resolution (e.g., 137.44 pixels).
• 😀 You can manually measure pixel distances by selecting the starting pixel and dragging to the endpoint, with the system displaying the calculated distance.
• 😀 The tool is useful for analyzing images to find locations and measure distances both in pixel values and real-world units, such as meters or miles.

Q & A

How can you access the pixel location in an image?

You can access the pixel location in an image by going to the 'View' menu and selecting 'Cell Coordinates', or by right-clicking on the image and choosing 'Say on Four Arguments'.

What information does the system provide when you click on a pixel in the image?

When you click on a pixel in the image, the system provides the x and y pixel coordinates, showing the location of the selected pixel within the image.

What coordinate systems are used to display pixel locations?

The pixel location is displayed in both the image pixel coordinate system (e.g., x = 1, y = 1) and the geographical coordinate system (longitude and latitude).

What does the imperial distance display when measuring distance in the image?

The imperial distance shows the real-world distance in miles and feet when you measure between two points in the image.

What does the metric distance display when measuring in the image?

The metric distance displays the real-world distance in kilometers and meters when measuring between two points in the image.

How is the dataset distance measured?

The dataset distance is the number of pixels between the two selected points, indicating the distance within the image itself.

How do you measure the distance manually within the image?

To measure the distance manually, click on the starting point of the pixels and drag your mouse to the endpoint. The software will then display the real-world distance.

What is the significance of the geographic coordinate system (UTM) in the script?

The geographic coordinate system (UTM) provides the real-world location of the selected pixel, translating pixel data into longitude and latitude coordinates for accurate geographic referencing.

What happens when you select a pixel in the image and increase its size?

When you increase the size of the first pixel, the x and y values remain the same (e.g., 1.1 for x and y), indicating the precise location of that pixel within the image.

How can the tool be useful for measuring physical distances or locations in an image?

The tool is useful for accurately measuring physical distances and determining exact pixel locations in images such as satellite imagery or maps by displaying both pixel and real-world coordinates.