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Getting speed and position data in TrafficSurvey Viewer using Georegistration - How to guide
Getting speed and position data in TrafficSurvey Viewer using Georegistration - How to guide

Get objects' speed and acceleration, use safety analysis, calculate headways and much more. DO THIS BEFORE SETTING ANNOTATIONS LIKE GATES!

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Written by DataFromSky
Updated over a week ago

In case you want to get speed and acceleration of objects in km/h or mi/h instead of kpx/h and export raw telemetry data, gap time and time to follow, turning movement counts, traffic region data, action region data including velocity information in km/h (mi/h), velocity visualization (km/h, mi/h), acceleration (m/s-2, ft/s-2), heatmap and headway visualization or work with safety analysis you should perform georegistration. By this step, you add the scale to your video and can access all the results in real-world coordinates. 

Disclaimer: Georegistration should be done BEFORE placing annotations like gates and zones. If you do not maintain this order, the position of annotations over the image will not be the same after georegistration and can cause "weird counts" if you don't fix this.

Remember that georegistration might be set in both videos processed by DataFromSky Light and DataFromSky Aerial, it is just necessary to keep in mind that some views from low-positioned cameras are not suitable for the extraction of accurate speed or distance data. DataFromSky wants to provide you accurate data and for that, we do strongly recommend you follow our guidelines for shooting the video from low positioned cameras, suitable for the DataFromSky Light service, and from drones, suitable for the DataFromSky Aerial service.

There are two ways of setting up georegistration:

  1. We are happy to set the georegistration for you. To do that, request it in the platform under the “Task” section or contact our team and share exact GPS coordinates of where the video was shot (a link to Google maps is sufficient). This service is paid according to the valid pricelist.

  2. Set your own georegistration in our DataFromSky Viewer.

What is the difference?

When the georegistration is done by our team, we do make special stabilization of the video that makes sure camera movements are minimized, then we can set georegistration per each frame of the video (if necessary) to be sure that location, speed, and distance data are precise. Then the results are sent back to you for further processing.

In case you decide to process your own georegistration, the automated stabilization is applied to your video as well (but without manual corrections that are sometimes needed). Then you can set your own georegistration for one “referring frame” of the video (the first one), so you can not influence movements of the camera which can lead to lower accuracy.

When is it good to set georegistration in your video?

DataFromSky Aerial

If you want to get as much accurate information as possible, try to reach the top-down view if possible and always follow our article with recommendations. Views suitable for the georegistrations are the following:

DataFromSky Light

In some cases, georegistration in a low-positioned camera video might be useful. For these cases, we have prepared an overview of use cases, where georegistration in DataFromSky Light might be used and data output might be sufficient for your analysis.

Always keep in mind that the position of the camera should be as high as possible, so you have an overview of the whole scene. Such as the following examples:

The first picture can provide you good data from the intersection area (without edges), second picture from the parking area.

Or you can use a perpendicular view to the traffic, so the perspective of the whole scene is more suitable for the identification of objects and their position.

Avoid following views, such as obstacles between the camera and the traffic that might disrupt the trajectory, too wide view that cause distortions at edges of the video, too low camera position, so one vehicle is covered by another one, or in general where you can not see the horizon, so distortion in the data might be higher.

How to set your own georegistration in DataFromSky Viewer?

To set your own georegistration in the DataFromSky Viewer, go to Tracking Log - Manual Geo-Registration...

A new window called Manual Geo-Registration Wizard opens. Follow this manual or read the following text.

First of all, you have to choose the region of interest to make sure you are getting accurate data. By blue polygon mark the road surface or other areas where you want to get the position-related data. DO NOT INCLUDE: buildings, grassland, forest and similar surfaces where no objects are detected. See an example of goof region of interest set up below.

To set georegistration correctly, you have to set at least 4 reference-points and you can choose whether to insert coordinates in UTM or WGS-84 system. These points should be set near places where objects are expected.

You can source the real-world coordinates from a map or from in-situ measurement. We recommend deploying an RTK GNSS receiver to get the most precise coordinates. Using mobile phones or standard handheld GPS devices is not accurate enough and should be avoided. Sourcing the coordinates on a map might be a better option.
For ground control points, select visually distinct and stationary features, such as traffic markings, road boundaries, etc.

One easy way to get GPS (WGS-84) coordinates is to use Google Maps. There, you can simply go to the location you want to georegister and right-click at the point whose coordinates you want to find out. This opens a menu—at the top of it, you’ll see the coordinates. Click them to copy them to the clipboard so that you can paste them into TrafficSurvey Viewer.

Inserted values for WGS-84 system should look like this:

Keep in mind that the latitude and longitude must be expressed as positive or negative decimal numbers (degrees). Positive latitude is above the equator (N), and negative latitude is below the equator (S). Positive longitude is east of the prime meridian, while negative longitude is west of the prime meridian (a north-south line that runs through a point in England).

If you want to insert the position of the video through the UTM system, insert your UTM Zone and Hemisphere and insert specific coordinates of each point in the video that you set.

Once you confirm the inserted points' values, a new window with the deviation of values is shown. These values should be as low as possible. We do not define maximum deviation because these values might vary based on the character of the video.

Confirm the georegistration process with the Finish button and enjoy position, speed and acceleration data in km/h or mi/h including other related functions!

We will be happy to answer any questions you may have. Contact us!

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