Georeferencing - Science topic

Yes, you can do this. Actually, its a broadly accepted approach for deformation monitoring using subpixel misregistration information and free data. Either you perform a moving window registration error assessment with some filtering or you utilize SIFT points and do the matching around. You can find a comparison in my paper list noted as 'Performance of correlation approaches...' If SNR is high, then subpixel misregistration assessment can be easily better than 1/1000 pixel.

Vishva Deep Singh

Hi :

To successfully export data from ESA's Sentinel Application Platform (SNAP) and import it into ArcGIS Pro, ArcMap, and QGIS, it's essential to ensure that the data is properly processed, georeferenced, and saved in a compatible format. Below is a step-by-step guide to address the issues mentioned:

1. Exporting Data from SNAP

Step-by-Step Export from SNAP:

2. Importing Data into ArcGIS Pro

Step-by-Step Import into ArcGIS Pro:

3. Importing Data into ArcMap and QGIS

Step-by-Step Import into ArcMap:

Step-by-Step Import into QGIS:

Here are troubleshooting Tips you may need :

Qgis, Grass GIS are two

Claro, aqui tienes

Yes 👍 💯 %…

Thank you @Gamal

You need to select specific projections in

georeferencing not a general coordinate system.

I hope this can helps you

Hello

Georeferencing is best when the cloud points are prepared (pre_GCP).

Because after ortho formation, georeferencing may cause parts to stretch.

Cheers

Dear Tomy Truong,

You can use QGIS, GRASS GIS, ILWIS. ENVI, ArcGis (Aacademic version) etc You need to find known coordinates for geo-referencing cross section maps of different scales. After that, digitize all the cross sections then change it into point clouds or dem using analysis tool.

QField can be useful for your purposes

Dear Ivan Marić,

Please check my Researchgate and you will find a paper that I published with my students using DJI phantom-4 for 3D mapping for part of the railway station at Khartoum-Sudan. We used the RTK-GPS to provide the ground control points. And we do have a case study in the paper.

Regards,

Gamal

the data is not supported by SNAP. The data is from the Chandrayaan-2 mission.

the refrence is the high resolution image SAR 36M

Then coregistration between the two images

U already got by Gabriel Asato .

Hello Martin,

Thanks a million. I did know the publication but had no idea, there was a download section.

All the best,

Micha

Hi Ghasem Askari , will try your suggestion...but using such approach the resulting georreferenced pictures will have a good accuracy only in them central parts. Isn't it?

Thank you Dear I put The data in excel chet and sent it

you can consider the mean, the standard deviation , or HSI of the colored image as features

Hello Akanksha! Did you get some soil texture map of India?

Referencing models with GCP is a great start, and if the GCPs are the exact same positions for both datasets, that is even better. To reiterate what I think your question is, you want to know 1) are GCPs enough for registering two datasets for topographic change detection, and if not, 2) is automated registration a better option for reducing error.

To make this decision, we need to know about GCP coordinate accuracy and the distribution and number of GCP. I will note that when I say coordinate accuracy, I refer to the accuracy of the instrument, such as GPS or total station, and not the accuracy reported within a photogrammetric project. If you have a lot of points (>10) and they are well distributed through your area of interest and your coordinate accuracy is high (~3 cm), then GCP is probably sufficient. If not, it may still be sufficient, you just need to test it with alignment for areas that likely have not have changed (invariant or pseudo-invariant points) or adjust you accepted minimum detectable change threshold - sometimes defined as the propagated error of your GCP (SQRT(error1^2+error2^2).

This error can be improved with automated registration, like the cloudcompare fine registration tool, but it can also exaggerate errors while telling you that registration improved. From personal experience, there can be some topographic distortion from photogrammetric datasets, especially if GCP are not well dispersed within your area of interest. This distortion will make automated registration adjust your clouds to have lower (improved) RMSE while giving them a poorer registration for change detection.

A good test for any registration is to look for apparent spatial trends in your data using a cloud to cloud comparisons. For example, in cloudcompare, run a cloud to cloud comparison and use the slider bar in the properties to look for patterns of vertical offsets. Recently I had one that showed the center of my area of interest had the lowest vertical offset and the amount of vertical offset increased as I moved away from the center. My options are to rebuild the cloud, choose a spot within the cloud that I want to focus change detection on or raise my accepted minimum detection threshold.

If you use an automated registration to improve registration error (I do this frequently), it is a good idea to do it on a subset of your data that you expect to have not changed during the detection interval. That will give you more confidence that you are not "over fitting" your point cloud, or trying to reduce RMSE at the cost of reducing topographic change where it has actually taken place. In cloudcompare you can test the original registration this way by unchecking the rotation boxes and set the drop down box to "Z". In general the cloud will not move, but will give you the same RMSE estimation. You can use that value to see if allowing rotation and translation improves RMSE significantly (as defined by you).

It's very important

Check out once at https://download.bbbike.org/osm/

Alternatively, if you can create a new layer at the https://www.openstreetmap.org/#map=5/11.178/34.761 and download the layers from bbbike site

Unless someone has already created the database, it is difficult to obtain...!

Hi,

RTK can deliver few cm accuracy. Few (4) GCP can help to further improve this accuracy. However, to use RTK need to know the coordinates of your (master) receiver on the ground. The station on the ground must have known coordinates to estimate (in real-time) the GNSS bias in that area and send it to the second receiver (rover) on the drone. The rover receives the corrections from the master and can therefore improve the accuracy of its positioning.

Considering the specific problem of RTK on drones we need to consider that:

1) the synchronization between GNSS and camera must be assured. If there is a delay between shutter and position recording, we will have systematic shifts between the 2 observations.

2) We need to understand where the GNSS coordinates refer to on the drone: in other words, has someone computed the relative position between GNSS antenna and camera? Do the recorded coordinates refers to the antenna or the camera?

Most of these issues are explained and discussed in:

Atmospheric correction should be done first because it is the first layer of influence that you can eliminate. Only after atmospheric correction, you are advised to play with your data.

Use exif tool

Dear Shahidul,

If you are using ArcGIS for mapping, try to change or define projection.

Type in search "define projection"

Or "project raster".

Alternatively you can use this:

ds = gdal.Open(filename_tiff)

gcps = ds.GetGCPs()

gt = gdal.GCPsToGeoTransform(gcps)

I think the reason why 'World Imagery Clarity' data that you added in ArcMap is not appearing under the 'Choose georeferencing layer' tab is because this imagery layer is a map service that is stored in ArcGIS online. I don't think you can georeference this online dynamic imagery layer. However, it may work if you export the image or take a screenshot and save it first. Needless to say the resolution would be reduced in such an attempt. Another question is, how do you decide which layer is more accurate? The existing layer or World Imagery layer?

Here is a similar discussion that you may find relevant https://community.esri.com/thread/107679

I agree with Mr.Luis, Landsat 8 and Sentinal 2 are good choise for NDVI study at a 30 meter resolution and high temporal resolution

Here are a few links. I hope this may help you.

With regards 

Amit

You can use MODIS MRT tool.  It has an option to reproject MODIS images in hdf format (sinusoidal projection) to the projection of your choice.  You can create subset as well as extract bands of your choice.

Thanks Augusto!!!

I am not familiar with arcgis (Is it a software) , but you could solve Weill- mechanical equation and determine chritical, sag which can happened according our National rules at -5o C degree with additional snow and ice burden or at +40 oC degree.

Hi Vincent,

When using Lambert93, the coordinates are affected by the scale factor of the representation Lambert93 =k=0.999051. So you must introduce coordinates without the scale factor as for example : X' =(X-Cte)/k, you use X'+Cte

If you just want to use the orthophoto, it may be be a good solution to use known structures as (x,y) GCPs (if well spatially distributed), but it may induce errors in the DEM...

Well, another way is to use ArcGIS software. In this software you can go to 'Spatial Analyst' then choose 'Convert' and then select the 'Raster to Feature' option. Under 'Raster to Feature' tool change 'Output Geometry type' to 'Point', select your geotif image under the 'Input Raster' option and finally save the output feature file and hit 'Ok'. 

Your geotiff image pixels will be converted into a 'point' shapefile or points. Next open the attributes of your point shapefile and add two new fields namely lat and long. Select the 'lat' column and  right click on it . Then from the drop down menu select 'calculate geometry'. Under 'calculate geometry' select 'Y coordinate of point' and select 'Unit' as 'decimal degrees'. Hit 'Ok' and your 'lat' coulmn gets populated with the corresponding values. Repeat the steps for longitude except select 'X coordinate of point' under the 'calculate geometry' option.

It has taken more words to explain the procedure, however if you follow this, it merely takes 2-3 steps and less than a minute to complete the procedure. The conversion may take some time to run depending on the size of your image.

 Yes all above answers are correct, Landsat image downloaded from USGS are georeferenced . It is in WGS84 projection  not in your country's projection parameters(specific). You can do projection transformation from WGS84 to your country's projection. Another way to do again georeference with your topographic map

I think it will help you

Dear Evans Ehouman,

You can export raster file to csv file using MATLAB or R tools.

Best regards,

Cherenkova Elena

Just a note of appreciation to Pinofor a clear, comprehensive answer. the only thing I would add is that the scale of the images is important in making the choice. Since these are drone shots and therefore presumably relatively large scale (local) I would think the Helmert would work but the TPS is certainly worth trying. In doing this it's often wise to (after making a copy of your image) trying it with two different transformations and then comparing the results. Use the one that best suits your needs.

Hey, I would suggest you to go with Python, it should be a script of a couple of lines.

Cheers

Hi Haron!

I often use OruxMaps. It is possible to load open street maps and to download google earth images in it. It also mark points with pictures.

Hello Dear Friend,

If you need really good precision, you need an RTK GPS system. The brand is not so relevant.

If you are not familiar with RTK the general idea is that you have a based station in a fixed position, and a Rover station that you carry around (or you pay a subscription to a National RTK network, to use their base stations). The base station and the rover station communicate with each other through an RF signal and so the precission is a few centimeters.

Of course this is expensive equipment..You need to set up a base station first which is time consuming, or you have to pay for a subscription to a national RTK provider.

So if the accuracy you are looking for is not so high , probably just use a D-GPS.

Ps: In my Faculty we are using some TOP-CON RTKS but all RTKS are good ...and expensive.

Guten Tag Antje,

I was tasked with this exact goal a few years ago.  I found this document very helpful, which contains links to free software and instructions on how to generate the networks and overlay them onto maps in google earth (which is great for presentations because you can rotate the globe around dramatically).  Also, they are RIS based.  Please read the attache document "Mapping the Geography of Science: Distribution Patterns and

Networks of Relations among Cities and Institutes".  Also might want to read " Mapping research networks" which uses a different approach and a free software called "Sonoma".  The second paper has a tutorial inside as well and the software is available at http://www.princeton.edu/~mnag/sonoma/

Hope that helps.

Viele GruBe aus Florida,

Alex

In addition to what has already been said about georeferencing, note that the Ground Control Points (GCPs), i.e. the set of homologous points you have to collect on the digitized image of the historical map and the current cartography, should be chosen as points which have preserved unchanged over time. As an example, if you can recognize the same building, pick up a points on its corners. According to the accuracy you want your final product to have, as current cartography don't use a raster map or a Google image (which can have large errors), but try to see if an official vector cartography (possibly at a large scale) is available.

After collecting GCPs, you have to choose a suitable georeferencing model. There are many models that you can choose from (and that you will usually find implemented in GIS software). The results of the transformation can be very different so be careful at which model you choose. To evaluate the georeferencing result, you should use some of the points you have collected as Check Points (CPs), i.e. points not used to compute the model but to validate it. A typically used statistics to evaluate the georeferencing result is the Root Mean Square Error (RMSE).

About the software usable to perform georeferencing, I can suggest the QGIS Georeferencer plugin (which however has some limitations) and the photogrammetric software PCI Orthoengine. The first is open source and available for free, the second is proprietary and available by paying the license.

I suggest two publications that better explain all my points and give you a practical example of georeferencing:

1) Brovelli M. A. and Minghini M. (2012) Georeferencing old maps: a polynomial-based approach for Como historical cadastres. e-Perimetron 7(3), pp. 99-110.2) Brovelli M. A., Minghini M., Giori G. and Beretta M. (2012) Web geoservices and ancient cadastral maps: the Web C.A.R.T.E. project. Transactions in GIS 16(2), pp. 125-142, DOI: 10.1111/j.1467-9671.2012.01311.x

Dear Vinod, 

Mr. Dierch reasons are correct. 

So if you have Erdas software you can solve this issues for 90%. 1St level we need to use, as per topomap projection(Keyboard method) after that you want to change set projection for Google earth image(Existing Viewer) or what ever it is. While we can reduce shifting both images.

Zone-to-Zone Extension accuracies are dependent on the derivative power employed by the transformation software.  Most software packages have truncations of the infinite series at the 7th derivative.  The U.S. Army had Extension Tables truncated at the 14th derivative and had/has accuracies better than 3 millimeters (Forward and Inverse) at plus or minus 45 degrees from the Central Meridian.  ESRI implemented the closed-form of the elliptic integrals several years ago, and their transformations are now good to fractions of a millimeter up to plus or minus 89 degrees from the central meridian.  See: (NOAA Technical Report NESS 81. Improved Algorithm for Calculation of UTM and Geodetic Coordinates. Jeff Dozier. Washington, DC. September 1980.)  However, there are numerous "typos" in the equations.

Hi Nilupul,

Aerial photographs need to be orthorectified and georeferenced. Orthorectification is about geometrically warping the image so that it becomes planimetrically accurate, and not a perspective image, which is what a photograph is. If you're using ArcMap, orthorectification and georeferencing are generally done together by establishing control points, minimizing position error measured by Root Mean Square Error (RMSE), and selecting a mathematical model for how much warping to allow in the image (i.e., a polynomial model). Have a look at:

I'm sure this is possible in open-source GIS like GRASS, SAGA, or QGIS, just haven't done it there myself.

Cheers, hope this helps,

P

Better use the official data:

I think that the answer of Kesoju is right.

As previous answers, you should convert coordinates into model's system.Then, since you have a lot of wells, I advise you to import a txt or dat file rather than put each single well by clicking on model's grid. It's pretty faster. I use Groundwater Vistas instead of Visual MODFLOW, and I can import txt and dat files (or shapefile when working with GIS system); it should be the same with Visual Modflow.

There is a rather vivid discussion of lab studies vs. field or in-the-wild studies within HCI and Ubicomp. It concerns mobile and ubicomp technologies particularly. The references below should help identify that body of work. It may not provide you with straightforward answers to your questions but may help you develop your method further.

Thank you Diogo. It looks very interesting

If we are known about x,y,z of two extremities of every cross-section, we could easily plot them as straight line from GIS and could be extracted in HECRAS using HEC GeoRAS. In hecras for every cross-section in geometry we could copy from excel the distances from left bank and corresponding elevations.

If you need just administrative boundaries I used http://www.gadm.org

It has a series of shapefile, with different levels of detail, for each country.

I know one app, "GeoFieldBook". It is specially designed for geologic mapping. You can take photo with iPad, record location, strike and dip, and some description. You can show all measured data on the map. However, I have not tried it in the field yet.