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Output coordinate system in geographic coordinates

Why can I not use WGS84 (Geographic Coordinates) as an output coordinate system?

Is this because coordinate systems can only be in m or f?

Is it because there is no projection on-the-fly?

Any ideas appreciated.

Will

Hi Will,

Currently, Pix4Dmapper can only export outputs in a projected coordinate system. This means that if your input coordinates are in Latitude, Longitude, Altitude, your outputs’ coordinates will only be in meters or feet, depending on the selected output projected coordinate system. 

You could use an external software to do the conversion (any GIS software)

I will transfer your need as a suggestion for improvement. Our Product Development Team will consider it for future version of the software :slight_smile:

1 Like

Thanks Christina, that’s sort of what I thought. 

 

Related question:
When I bring in gcps as lat/long from csv, it only gives 3 decimal places of precision. Is there a way to allow more decimal places of precision in lat/long coordinates?

Hi Will,

Pix4Dmapper takes into consideration all decimals. If you open the p4d file with a text editor, you will see all decimals. It is a display issue that we have in the GCP Editor that gives the impression that only 3 decimals are taken into account. We should solve the issue :slight_smile:

Can pix4dmapper covert (X,Y,Z) coordinate system to WGS84 coordinate system. If can, how do it?

Thanks so much

Hi Thanh,

As mentioned above, Pix4Dmapper can only export outputs in a projected coordinate system, so the conversion allowed is the other way around: from a geographical coordinate system (with angular unit) to a projected coordinate systems (with linear unit for X,Y,Z). For more information, please read our Pix4D article: https://support.pix4d.com/hc/en-us/articles/202558099-Menu-Project-Select-Output-Coordinate-System

Cheers,

Teodora

Hi Teodora

Thank you so much for your reply

So I don’t clearly understand for “Vertical coordinate system”. When i import images have geolocation taken uav so which “Vertical coorinate system” i can chose? The same with “GCP/MTP manager” and “Output coordinate system”. 

And could you explain me for “ESPG”

Thanks

Hello Thanh,

The vertical coordinate systems available in Pix4Dmapper are: three geoid models (egm84, egm96. egm2000) and the ellipsoid of the selected horizontal system. For example, a project with horizontal coordinates based on the ellipsoid of WGS84 can have vertical coordinates based on the ellipsoid of WGS84 (GRS80) or based on one of the geoids (egm96 is the default option). The same applies to any other coordinate system.

If you need to select a different vertical datum then you should either provide the offset between the desired datum and the ellipsoid of the selected horizontal coordinate system or select the option Arbitrary Coordinate System for the outputs and the GCPs and import GCPs with coordinates in the coordinate system you specified.

In the first case, you should know the shift/offset between the current vertical coordinate system and the target coordinate system. This shift can be added in the Geoid Height Above XXX Ellipsoid option. You can find more information about when to use the Geoid Above the Ellipsoid Function here: https://support.pix4d.com/hc/en-us/articles/211739726-When-to-use-the-Geoid-Height-Above-the-Ellipsoid-Function

In the second case, the software will take the GCPs values into account and will try to fit the model as optimally as possible to these GCPs. Then, all your outputs will still be in an arbitrary reference system but this system will be based on the system defined by the GCPs. 

An EPSG (originates from European Petroleum Survey Group) is a unique code for any coordinate reference system utilized all over the world for creating maps. For instance, the EPSG code for WGS84 is 4326. You can read more about EPSG on this website: http://epsg.io/

Cheers,

Teodora

Hi, for basic GCP/MTP editor how do i change the X,Y in meter to lat,long in degree?

Hi, The coordinate system that is chosen is a projected coordinate system that is defined in meters. To use latitude and longitude in decimal degrees you must choose a geographic coordinate system from the list. I anticipate that WGS 84 is the correct coordinate system. To change your coordinate system, select Edit… and then choose “WGS 84”, in meters. It will likely be all the way at the bottom of the list. Accept the changes by clicking OK.

ohh i see, thank you very much for the help!

Btw, i have another question. it seems my rmse is wayy too high. is there any way i can adjust the gcp marking manually while checking with the error before i start to reoptimize again?

Can you send me the full quality report?

basically i want to move the marking on the picture while checking the “error to gcp initial position” so that i can lower the gcp error

sure!

gcp error.pdf (1.9 MB)

As you can see, your projection error for each GCP is too high. Projection error is an indicator of how well you have marked your GCPs in your images. You want your projection error to be under 1 pixel at a minimum but ideally under .5 pixels. In the image below you can see your GCP’s reported projection error, all of your GCPs have been ineffectively marked in your images.

You want to mark your images in 8-12 quality images where you can confidently identify the center of your target, do not use the automatic marking feature. You need to go back and mark your GCPs how I have described above, reoptimize your project, and then reprocess both steps 2 and 3. Before you run steps 2 and 3 you should read your quality report to see if your new marks have a projection error that is within an acceptable threshold. You can generate a new quality report after you have reoptimized your project by going Process -> Generate New Quality Report.

understood! but i think i have marked it correctly. however, do you have a suggestion on what should i do when marking? as in, should i rlly zoom into the gcp or doesnt rlly necessary? as long as i just mark it in the middle

If you are certain that you are marking correctly ( I mean you can see the center pixel ofthe GCP target), then you should zoom in. That gives more weight to the mark

alright thank you very much!

Btw i have another question. why does the output coordinate system is in kertau? doesnt it have to be the same? which is wgs?