Lecture 12

[Music] hello everyone so in this lecture we will give you a demo on the qgis how we can uh do the GE referencing with the help of the qgis platform here we have uh written some of the U steps to do the GE reference on the qgis platform so first you have to open the qgis so when you will open your qgis so first you have to add the uh the Topo sheet we will show you how we can do the GE referencing with the help of Topo sheet so Topo sheet is a image so you have to go to the raster format because the image is in raster format so you have to browse your image and here we have one Topo sheet for the uh chandigar region that is the uh uh fot Jone of the Himalaya so here you can see the uh this is the uh chandigar region and here you will uh this this image is not GE reference so for you have to first to G do the GE referencing you have to uh zoom up uh the uh one of the corner of this Topo sheet so here when you will zoom zoom in so you can see that here is your longitude and latitude is written over there so this uh for this point your uh longitude is 76° and 45 minute and the latitude is 31° and 0 minute to uh so to do the G reference uh of this image AG so the on the qgis there is one plugin so you have to go to you have to open that GE referencing plugin that is called the GE referencer and you will get the that GE referencer over the raster option so you have to go to the r option and here you can see the GE referencer option so it is uh the sign is uh written over there so you have to just click the G referencer and when you will click the G referencer you will get such type of bindo and uh you have to because you want to do the G referencing of the Topo sheet so you have to open your Topo sheet over there so to open the uh Topo sheet you can simply uh click uh on this open raster image so you can do the GE referencing only the uh rter file formats so that's why here you can see that you don't you don't have any other file format such as VOR or delimited or the WG uh WMS so those options are not available here here you can see only the raster format option so when you will click on this raster format option they will ask you to open your file so I have opened the file here so you can simply uh do the uh you can simply go to the uh one of the corner of your Topo sheet so I will start from the left top corner of this Topo sheet so to zoom uh zoom in or zoom out you have to Simply click on your uh the control button of your keyboard and you have to scroll up uh with the help of your mouse so and to zoom out you have to uh uh similarly you have to uh scroll down with the help of your mouse so here I have zoomed in uh to that uh uh that point so here you can see the 76° 45 minute and 31° 0 minute latitude so to do the GE referencing here you can see there are uh some of the options are available so here you will uh you will also see the add Point option and then delete point so with this add point you can simply add point on your your map so I will first go to the add Point option and then uh I will go to the uh uh the point where I want to add the point this point are basically the gcps which I explained in the last lecture so first I have to add the gcps so I will just go to the this point where I know the exact latitude and longitude so when I will click over there so your window will open and it will ask ask you to put the latitude or longitude in terms of X and Y so you have to give here the latitude and longitude so now you have to click over there and when you will click over there you will uh your window will open and here they will ask you to enter the latitude or longitude in terms of X and Y so here you can simply put your values uh the longitude is 76 and 45 minute and your latitude is 31 and 0 minute and you you you just click okay and here uh at the uh bottom down uh of your screen here you can see the your point has been marked and you can see the ID Source XY and your the associated uh now the error is not showing over here when you will Mark all your point then your residual error will show here so the if suppose this uh this option is uh not showing on your window so you can enable the GCB table by simply clicking over the panel option and your gcp table here you can see this is enabled that's why it's showing over here but in case if I disable this option now you can see you cannot see your GCB table so you can uh enable your GCB table through the view option so I have marked one gcp from the uh top left corner of uh this Topo sheet now I will go to the second corner you simply zoom out by uh scrolling your mouse and then again zoom in to your uh uh the second uh uh second corner of of your Topo sheet now here you can see your longitude is 77° and 0 minute and your latitude is 31° 0 minute now I will choose this point as my second control point so uh I want to Mark the second control point on this point so simply you have to click and similarly you have to enter the longitude and latitude so my long itude is 77° and 0 minute and latitude is 31° and 0 minute now I have entered the latitude and longitude and Mark my second gcp now I will go to the third Corner that would be the bottom bottom down corner of the Topo sheet so so here you can see here you can see your latitude is 30° 45 minute and your longitude is 76° 45 minute so you can add this point as your gcp so I will enter the longitude 76° and 45 minute and latitude is 30° 45 minute now click on okay so my third gcp has been marked and now I will go to the fourth Corner that would be the right bottom corner of the Topo sheet here you can see your latitude is 30° 45 minute and longitude is 77° 0 minute so I will just enter this value and click on okay so my four point has been marked so here you can see this point has been marked as the uh control point now I can choose my uh polinomial equations and the resampling uh method by going to the setting option here you can see the transformation setting is given so by uh now when you will go to the transformation setting you can see here you have to select your transformation type so which type of transformation I want to use so here I would say that you have to uh uh Shuffle uh some of the option here you can see the linear helmet polinomial one 2 3 thin plate spine spline and projective so I will start with the linear and nearest never resampling method so my target uh reference system is so here I would I would choose the uh wgs84 43 26 epsg uh projection system so this is uh uh most commonly used uh geographic coordinate system in uh one of my last lecture I have explained you uh what was the wgs84 so this this is the uh B geod coordinate system and this uh uh uh this considered the Earth uh Center as a uh uh Point uh the reference point through which all the latitude and longitude has been calculated so I will choose this option or if you want to uh uh uh choose some other projection system or the datam that you can uh choose by going uh this option coordinate reference system selector and you can simp simply search uh over here which coordinate system or which uh uh datam or uh uh transformation system you want to use for your map that you can use for this case I will choose the wj4 43 26 projection system now in in another option you have to give the output for your image file here you can see by default it has been saved my uh saved uh on the location where my raw image was saved with the slight modification with the uh with the naming of the image so I will uh you can uh do the changing if you want to uh change your uh output raser name that you can do and the another thing is you have to just click the save gcp point so the gcps or the control point which you have marked that you can save by enabling this option if you are not saving your gcps so in that case your the point which you have marked that will be deleted once you closed your this G referencer uh uh uh window so now I will click on okay so here you can see so this this uh this red lines are basically showing the error here you can see now once when I have chosen my polinomial equation and sampling method so here at the residual option here you can see these are the associated error for my pixels now I will just go to the transformation setting again and now I will change the linear to helmet now I will see what what will happen so here you can see your error is very higher for this helmet option so similarly you can just Shuffle these options and you can see which polinomial equations are suitable for you so I will keep it uh with this linear and nearest neighbor and to do the GE referencing you can simply uh click on the start GE referencing option so when you will click on the GE referencing option now here you can see rter was successfully GE reference when you will minimize uh minimize this G referencer option so uh when you will minimize this ge referencing option and here you can see these are the point which you have marked so this is the uh true geographic coordinate system here you can see the 77° and 29 uh latitude and 77° longitude but you cannot see your GE reference image over here so there is another option in your uh ge referencer where uh you can uh you can directly load your GE referencing image over the qgis platform so you have to for that you have to enable the load in qgis when the uh G referencing is done and uh if you have not enabled this option you uh although your image has been GE referen and it it has been saved over here which you you have uh assigned the output uh uh raster image path in that on that path your image is already saved but if you are enabling this option so this will automatically load your GE reference image on the uh GIS platform so now I will again click on the G referencing option and now you will see that your image has been already so this was your un reference image and this is your GE reference one so so here you can see that your image has been Geo referen and that you can you uh here you can see that the true uh longitude and latitude of the your image you will move your cursor over the image and you will see that your uh latitude and longitude has been changing so this image has been GE reference and you can also verify your GE reference image by enabling the base map just below this image so that you can do by adding the base map to add the base map yesterday we have uh to add the base map we have uh shown you in one of the lecture that how you can uh add the base map on the qgis for that you have to go to the web option and in quick map service so in our last lecture uh we we have have show uh shown you that how you can add the base map uh by searching over here but there is another option and through that you you will be enabled the Google satellite images over here now you can see here you cannot see the other satellite data except NASA and osm so you can add all the images through uh by clicking on the setting option and in the mode service in mode service you you have to click the get contributed pack and your uh other satellite data will also add in your quick map service so for that you have to just uh get the internet access and first make sure that your system has a uh uh internet connectivity and then uh when your uh system is uh having the internet connectivity your your pack will be automatically downloaded to the quick map service to get this uh all the satellite package first you have to make sure that your PC has a uh internet connection and once you uh connected with the uh uh internet your PC has the internet connection then you just go to the get contributed pack and your uh here you can see the last version of contributed pack was downloaded now you just close this window and and go to the web web option so once you downloaded the uh your uh web pack and then you will go to the web and quick map service now here you can see first it was the only NASA and osm now here you can see that all the satellite data uh which are provided by different organizations that you will uh get over here for example if you you want to use the Google satellite data now here here you can see all these uh data which which are provided by the Google that you can get from here so now simply we will load the Google satellite so you just click on the Google satellite and on the layer panel you can see your Google satellite image has been loaded you can zoom out your window and you can see all the Google Images has been provided over here so you just go to the uh go to the your image for that you can just uh click on the image uh right click on the image and you can use this Zoom to the layer option so when you will click on the zoom to the layer option it will direct you to the your image so here you can see your image has been Geo referenc uh properly and uh to uh you can uh you can also use the swiper tool which we have uh uh install in one of our lecture so you can use this swiper tool to swipe your image and see that how accurately your image has been Geor referenced so you can just drag your swiper tool now you can see over here the boundary of the hilly terrain or the flat portion you can see and it is uh it is accurately Geor reference you can see over here this portion the mountain where sub Himalaya has been uh uh started uh where the S Himalaya and the indog gtic plane are meeting you can see this area and uh with this uh swiper tool you can check whether your image has been uh properly GE reference or not if suppose your image has been not Geor referenced properly or accurately you can again go to the Geor referencer tool and you can add some more ground control points and that uh Ground Control point will help you to uh ge reference accurately your image so uh you can use this ge referencer tool and you can uh Geor reference any of your Maps or images so in the uh now we will see that how uh we can GE reference a uh uh a map or image uh with the help of the base map so till now we have understood that how we can GE reference a topo sheet which has already assigned some coordinate informations and now we will uh look or we will explore the GE referencing uh option uh to GE reference such kind of map which don't have any geographic coordinate informations so we will GE reference such uh a map uh with the help of the base map so uh first you just remove this map to remove this map you just right click on the map and you uh click on the remove layer option so this will uh uh you have to uh again confirm uh the remove option and you see here you have remove your uh your map from the uh uh uh this software so you close this G referencer option so to close the G referencer option you just go to the file and you close G referencing so now and you enable this Google satellite image so it will bring your Google satellite map on the uh your screen so now I will load uh a map which don't have any geographic coordinate information so uh I will GE reference that map with the help of this Google satellite image so we will see how we can do that so you have to first open that image so to open here I have one uh one image of CET Band F and you open this image this is uh image is open in the layer option but you cannot see on your screen so to to see your image you just right click on the image and click on the zoom to the layer option now here you will see that this image is open on your screen so so here you can see that image because the your CTO set image has already assigned some uh uh geographic information but it is not accurately correct so you can uh correct this uh image and assign uh the geographic information accurately with the help of the Geor referencing option so if you use this swiper tool you can see that this this image is not accurately correct see this River this river is uh the the River on the on the image is is place somewhere else irrespective of your base image so we will do this correction with the help of GE referencing tool so first you have to go to the raster option and you just open your GE referencer tool and load your data on the GE referencer so I have loaded the data here uh you can just uh enable the add control point and with this add control point you can uh Mark The Ground Control point or gcp on both the images to Mark the gcps you to Mark the gcps you first have to identify some point which are similar on both the images so so you just go to the uh your satellite image and here you know that your image is for this particular area so you have to identify some common points or some common uh control point where uh those points are similar or you can easily identify on both the images so you can see you just uh zoom in a little bit or you can see this is the these are the two rivers and here you can see here this is the road or this is another road and this is the intersection point of the two road so you have to identify this intersection point on your base image also so go to your base image or you just zoom in here you can see this is the same area which we have uh seen in in our Target image so you can choose this this point as your ground control point so you go to the GE referencer and you add the uh uh Point by clicking over here and now this will ask you to put the latitude and longitude but this Geor referencer has one uh uh one option where you just uh this will direct you over the base map so from this this from map canvas option when you will click over here so this will direct you to the base map so you don't need to enter the latitude or longitude over here if you know the uh exact latitude or longitude of this position or this point then you can put over here uh as we did for our topographic map but for this uh case you can just uh go to the Bas map and you can click over here so this will you can see here your uh longitude and latitude is automatically mentioned once you click over your base map so now you just click okay and here you can see one gcp has been marked similarly you have to again identify the another point where you can mark your uh control point so you just go to the base map and you identify the another point so here you can see this is another River and here this is the Road intersection so try to identify those point which are easily identify uh easily you can identify on both the images so uh that would be better because if you are uh selecting point which are not easily identifiable in both the images in that case if you are mistakely uh selecting Point uh here and there so that will ultimately associate some kind of error and that will uh uh uh means your uh that will uh ge reference uh your image but your image will be uh uh getting some error so you choose this point and click over here and go to the map and you can see this is the this is the Road intersection which we have chosen in our Target image so you also click on this uh base map once you click you can see this uh longitude and latitude is mentioned over here for this point and now click okay so we have marked the two point and so and you have to mark another point so at least uh try to Mark 4 to Five Point uh to G reference your map and uh you just try to scatter those four four and five point because if suppose you are uh choosing point in a particular particular area or your point has is clustered for a particular reason so that will also associate error in your GE reference map so here you can see is it's a dam so you just you can choose uh one point from here so this is your uh this is your Dam and this is the road so you just try to identify this point on your base map you just scroll and here you can see this is the point and this point you can Mark so this is the uh corner of the uh road so I will choose this point as my control point so you just click on uh click on here and you can see this is your latitude longitude so we have marked the three point so I have to choose another point so you uh you go to the another corner and here you can see this is one road and you try to identify this road on your base map so this is the river how you can identify your uh uh your uh point so you have to just uh see the geomorphic feature of your image so for this case I can see that this river is coming from here and this river is passing uh this road so you can choose this point so first you can you you have to locate this point on your map so this is the this is the uh point where we can mark the point so this is the uh over Bridge so I will choose point on this over Bridge so here you can click and from the map section you can click over here so now you can see we have marked the four point and you can also Mark one another point at this Center portion because uh here we have marked the four point on the four corner of the image and one more point will give give us the more accurate GE referencing image so here you can see the Another River the small uh River it is Flowing uh from here and you can see this is uh a road so you have to just identify this point on your base map you can see this this road you have to identify on your base map here two Road are uh Crossing each other so I will identify this point on the base map so you just go your base map and here you can see this is the point I can Mark uh the control point over here so you just Mark here and you can see so now we have chosen five point and with the help of this five point with the help of this five point we will do the G referencing so we have completed with our uh uh gcps so at the uh gcp table you can see Five Point has been marked and in the residual error option you cannot see anything so to get the residual errors you have to first choose your polinomial equations and the resampling method so to choose the polinomial equation and resampling Method you have to go to the setting option and transformation setting you have to choose your polinomial equation so I will start with the linear and nearest neighor and my target coordinate system is wgs84 43 26 because this is the CET image and the CET image has been acquired with this uh wgs84 datm system with reference to this wgs84 reference system and my output uh image has been is saving on this uh directory and I have also enabled the save gcp point and load in the qg GIS when done so just click on okay and here you can see this much is the error associated with your image with this transformation setting so you can just Shuffle this transformation setting and you can see what happens so for this image you can see that the transformation setting of polinomial Bor and nearest neighbor is giving me the minimum residual error here you can see the residual error so you try to shuffle all these option and see uh which uh transformation type and resampling Method giving you the minimum residual error so you choose that option because every image has been Associated some kind of error so you might uh not know that which uh image has what kind of error so for that you have to just simply shuffle all the options and you can go through the this option and whichever is giving you the minimum error so you try to choose that option so for this image I can see that this polinomial one and nearest never resampling method is giving me the minimum error so I will go with this option and you just click on the start GE referencing option so this will your image is uh ge referencing and once the G referencing has been done you can see one popup will come up here and you can read that raster was successfully G reference and uh because I have enabled the uh load in qgis option so your image might have open in the in the your uh uh screen on the qgis screen so here you can see this is your band app modified this this is your GE reference image so this black patches are basically the portion which don't have any kind of DN values so that's why this is uh this portion is showing you black so you can uh use your map swipe tool to see that how accurately this image has been GE reference so you can see over here you can little bit Zoom this image or you can see that this river is perfectly align over your your base map so this image is accurately GE reference so similarly you can Geor reference your Topo sheet or any kind of map which don't have any kind of geographic uh coordinate information so you can uh use the gis platform uh here uh we have shown you or give a demonstration on the qgis uh as well as the arcgis so uh uh uh with this uh both these GIS platform you can uh Geor reference your images so in next lecture we will uh came with a uh uh we will come with a third lab where we will show you how we can do the merging and mo mosaicing of different images with the help of uh uh this qgis thank [Music] you [Music] [Music]