# Georeference issue **URL:** \ **Category:** PIX4Dmapper\ **Created:** [August 12, 2022, 8:43pm UTC](https://community.pix4d.com/t/georeference-issue/23559 "2022-08-12T20:43:47Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![Xliu2014](https://avatars.discourse-cdn.com/v4/letter/x/a6a055/32.png) [@Xliu2014](https://community.pix4d.com/u/Xliu2014)\ **Post date:** [August 12, 2022, 8:43pm UTC](https://community.pix4d.com/t/georeference-issue/23559/1 "2022-08-12T20:43:47Z")
Hi, So this summer I’m collecting images weekly. I’m wondering if I can use the early referenced orthmosaic image to geo-reference the latter images, such that I don’t need to georeference the images with GCPs each time? Suggestions would be appreciated. Thank you for your time. ---
**Author:** ![Nikoleta\_Dimopoulou](https://avatars.discourse-cdn.com/v4/letter/n/53a042/32.png) [@Nikoleta\_Dimopoulou](https://community.pix4d.com/u/Nikoleta_Dimopoulou)\ **Post date:** [August 15, 2022, 4:55am UTC](https://community.pix4d.com/t/georeference-issue/23559/2 "2022-08-15T04:55:15Z")
Hi @Xliu2014, To georeference a project you will need GCPs. _Georeferencing_ is the process of assigning real-world coordinates to your results. **Ground Control Points (GCPs)** are points with known coordinates and they are used to accurately georeference a project to assess the accuracy of the reconstruction, so I would say this is the only way to georeference a project. Best, ---
**Author:** ![Xliu2014](https://avatars.discourse-cdn.com/v4/letter/x/a6a055/32.png) [@Xliu2014](https://community.pix4d.com/u/Xliu2014)\ **Post date:** [August 15, 2022, 5:44pm UTC](https://community.pix4d.com/t/georeference-issue/23559/3 "2022-08-15T17:44:10Z")
Hi Nikoleta, Thank you for your reply. Another probelm I got while georefencing iamges with GCPs for each flight date- the final orthomasic image for each flight date shifted in space with one the other. So the are not spatially 100% located at the same space. That’s also why earlier I asked if I could use an image to georefence another image. Is there any suggestion to elimate this spatial displacement? ---
**Author:** ![Nikoleta\_Dimopoulou](https://avatars.discourse-cdn.com/v4/letter/n/53a042/32.png) [@Nikoleta\_Dimopoulou](https://community.pix4d.com/u/Nikoleta_Dimopoulou)\ **Post date:** [August 16, 2022, 1:12pm UTC](https://community.pix4d.com/t/georeference-issue/23559/4 "2022-08-16T13:12:12Z")
Hi, Could you share with me the quality reports of the projects and maybe later the orthomosaics? Best, ---
**Author:** ![Xliu2014](https://avatars.discourse-cdn.com/v4/letter/x/a6a055/32.png) [@Xliu2014](https://community.pix4d.com/u/Xliu2014)\ **Post date:** [August 16, 2022, 3:28pm UTC](https://community.pix4d.com/t/georeference-issue/23559/5 "2022-08-16T15:28:20Z")
Hi Nikoleta, Thank you for your reply. It seems like the images are too big. So I uploaded a copy to google drive (as the link below). Please let me know if you have any questions. [https://drive.google.com/drive/folders/1nXZG3XhBgTWJEplbpeW8M9MF8uaYcXVn?usp=sharing](https://drive.google.com/drive/folders/1nXZG3XhBgTWJEplbpeW8M9MF8uaYcXVn?usp=sharing) ---
**Author:** ![Kapil\_Khanal](https://sea2.discourse-cdn.com/pix4d/user_avatar/community.pix4d.com/kapil_khanal/32/304_2.png) [@Kapil\_Khanal](https://community.pix4d.com/u/Kapil_Khanal)\ **Post date:** [August 18, 2022, 4:51pm UTC](https://community.pix4d.com/t/georeference-issue/23559/6 "2022-08-18T16:51:23Z")
Hello @Xliu2014, Regarding your first question, **I’m wondering if I can use the early referenced orthmosaic image to geo-reference the latter images, such that I don’t need to georeference the images with GCPs each time?** You can’t georeference the later orthomosaic using the reference from the initial georeferenced orthomosaic. The best thing is to have the GCPs in all the projects so that they align with each other if you are comparing multiple flights. If there are some objects or markers that are present in all of your projects then, you can extract the geolocation of that markers ( from the old project that was georeferenced) and use it as a GCPs on a project which doesn’t have the GCPs. ---
**Author:** ![Xliu2014](https://avatars.discourse-cdn.com/v4/letter/x/a6a055/32.png) [@Xliu2014](https://community.pix4d.com/u/Xliu2014)\ **Post date:** [September 8, 2022, 6:45pm UTC](https://community.pix4d.com/t/georeference-issue/23559/7 "2022-09-08T18:45:55Z")
Hi Kapil, Sorry for the late response. I was sick and off-office for 2 weeks. Thank you so much for your answers. Here I have another question, when I geo-references with same GCPs for each flight date, the orthomosaic images are having some shift from each other (as in my previous post replying to Nikoleta). So they don’t locate at the same place. I wonder what I should do about this? That’s also why I asked earlier if I could use one original orthomosaic image to georeference the latter ones. Thanks for your time. ---
**Author:** ![Kapil\_Khanal](https://sea2.discourse-cdn.com/pix4d/user_avatar/community.pix4d.com/kapil_khanal/32/304_2.png) [@Kapil\_Khanal](https://community.pix4d.com/u/Kapil_Khanal)\ **Post date:** [September 8, 2022, 7:55pm UTC](https://community.pix4d.com/t/georeference-issue/23559/8 "2022-09-08T19:55:15Z")
Hello @Xliu2014, If you are using a permanent marker for the GCPS, there shouldn’t be a shift on your orthomosaic. If it is happening, then either those GCPS markers are not in the same location, either your project or the GCPs were processed well, or there is some issue with your workflow. ---
**Author:** ![Xliu2014](https://avatars.discourse-cdn.com/v4/letter/x/a6a055/32.png) [@Xliu2014](https://community.pix4d.com/u/Xliu2014)\ **Post date:** [September 8, 2022, 8:12pm UTC](https://community.pix4d.com/t/georeference-issue/23559/9 "2022-09-08T20:12:44Z")
Kapil, thank you for the quick response. The GCPs are permanent, fixed by spikes to ground. I’m using the same GCP file for all the projects. So the possibility like you said would be that from workflow. However, I’m using same template. I’m wondering if there’s issue in the workflow of mannual tieing of the GCPs to the images. I’ll spend some time to investigate this and keep you posted. Thank you so much for your consideration.