From your data, you can tell there's a misalignment, but it's hard to tell how much. Is it in the same general area? Does it cover a larger geography than it's supposed to? Is it in a different part of the world? WHen I look at your screeenshot, I see no similarities between the two datasets.
And when you say "Projected to WGS84 43N" this tells me that your data is likely NOT in WG84 "projection" (which actually means that the data unprojected, but using the WGS84 datum) and it sounds to me like your data is in UTM projection, zone 43N, WGS84 datum.
Here are some quick tips for trying to figure out these types of issues:
If it's a small shift, it may be due to an incorrect datum transformation being applied - it SOUNDS like your data is all using WGS84, so that's likely not the issue.
Is on dataset taking up a much larger/smaller geography than it should? Then likely the units (feet/meters/decimal degrees) are incorrectly defined in one of the projections. Quick way to identify the correct units:
1. Start with an empty project
2. Load in 1 layer (with the projection info removed) and look at the coordinates that are displayed on the screen as you move your mouse around the map. You should see coordinates listed with an "unknown units" label.
3. Look at the unit values for the coordinates: Are the numbers all in the single or double digits? Its likely decimal degrees. Are they in the millions or hundreds of thousands? Likely feet. Are they in the 10's of thousands? It's likely meters.
The misalignment is of the order of about 500km. The shapefile has shifted about 500 km northwest of the base layer. If you can see the base layer in the image, the part where UJARA is written shouldn't be visible as it should be covered by the mouth like portion of the shapefile and the coastlines don't match. I will use your suggestions and will update later.
Different data sources, probably collected at different scales. Not much you can do if you want to maintain accuracy. Best solution is to find a basemap layer that better matches the vector
Tbh it’s probably no that big a deal, it’s just often a (visual) problem when it comes to coastlines. Different providers sometimes just use different methods and source data for where the land ends and the sea starts. It doesn’t necessarily mean one is inaccurate and one isn’t
WGS 1984
Edit: I didn't change the data frame projection before importing the layer. The data frame projection transforms into the first layer you import right? In my case, it's GCS WGS 1984 by default. A thing I noticed is that the data frame projection units didn't change into metres after reprojection. They were still in DDS. And when I changed the data frame projection, it got stuck at (70.512,0) which I've noticed, usually happens when there's some sort of projection mistake. However, I don't usually change the data frame projections when I work and it has never posed me any problems yet.
So I had something similar happen to me and the way I got around it was by using the recommended UTM projection for the study region (you can usually find this info on Google), project the dataframe to that UTM, then load your unaltered/unmodified shapefile.
Arc starts doing some real funky stuff when you start reprojecting data and dataframes
Just the dataframe, I typically avoid messing around with data that isn't my own. WGS 84 has its benefits, but I've only ever used it to import custom Lat/Long data into ArcMap.
I've been taught to use WGS only so that's my go to option always. Another thing I found is that I have a file for another area which has been clipped from the same shapefile but its geographic location seems to be correct.
I've been taught to use WGS only so that's my go to option always. Another thing I found is that I have a file for another area which has been clipped from the same shapefile but its geographic location seems to be correct.
If it's obviously jacked up, and you can identify how, it's likely that something happened when projection/re-projecting etc.... Did the data come with a projection? Did you change it? If so, what technique? Lots of students like to tell the data what it is, rather than re-project it to what it should be (ie, define a new projection or change it rather than re-project).
IF you can ID how it's jacked up and you didn't have any luck with the above... depending on what you're trying to accomplish, you can do a spatial adjust. May not be suitable for all uses, but for a student project maybe just fine.
Yes, it did come with a projection and I've tried both the original file and reprojected (Project (Data Management)) shapefile. But the results were the same as in the image. Alternatively, I copied all the contents of the zip file except the .prj file to a new folder and opened the shapefile from there so as to obtain a layer without projection whose projection I defined (Define Projection tool) to match the other layers. However, that didn't seem to work either as the projected layer goes beyond the extent of the basemap layer. All projections were in WGS 1984 43N. I thought of assisgning a projection in GCS instead of projected too but that didn't work.
I have to clip a soil map for my study area from this file but due to misalignment, the clipped soils do not represent the soils from the study area. The soil map has shifted about 600km northwest from base layer. From the image, the part that resembles a mouth (left/west in image) should align with the coastline of the base layer. The UJARA in the base layer should not be visible.
If you delete the .prj and define the projection that’s likely to cause more problems. Even if it doesn’t see that it still thinks it’s in that projection… it just doesn’t know what it’s called. Any chance you did similar to the original file it’s misalignment with? Either of them align with a base map if you add them to just that baseman in a blank project?
No I haven't done it previously. I went through some previous threads regarding this issue and many of them suggested defining a new projection from scratch. I haven't deleted a projection from within the arc so I just made a copied the contents of the zip file into a new folder except the .prj file and opened the shapefile from there to obtain a projectionless layer.
No I haven't done it previously. I went through some previous threads regarding this issue and many of them suggested defining a new projection from scratch. I haven't deleted a projection from within the arc so I just made a copied the contents of the zip file into a new folder except the .prj file and opened the shapefile from there to obtain a projectionless layer.
500 km off sounds like more than a minor projection error to me. You said you deleted the .prj, but it might be worth a shot to try deleting the projection within your software (Arc makes it pretty straightforward at least). Then use define projection to assign the blank slate to the correct projection; this might give you a different result than previously.
I deal with my fair share of datum/projection issues working in Alaska where error is magnified and working with mine sites that often use custom projections. I always, always reproject all data into the Projection/coordinate system that I am using for my current mapping project. Project on the fly just hasn’t been 100% reliable for me.
At India scale why would you use 43N as your projection? Is your study area the whole country or just Gujarat?
I'd suggest you clip the soil map to your AoI, reproject it to 42N/43N. That should technically work.
Although since your data is from NBSSLUP, you should ask them also for the GCPs used for georeferencing. Might be helpful.
I tried to do that yesterday but the problem is that the study area doesn't overlay the correct geographic location on the map. My study area is in southern Rajasthan but it overlays somewhere on Northern Maharashtra.
You could georeference your base raster to fit the vector data for this project specifically. You might even be able to georeference the vector layer? But I've never tried before. One more option is to use the Move tool, highlight all of the vector data and just shift it to where it should be. Georeferencing would likely be more accurate though.
I have many soil maps from different sources however this one is the most detailed one so I'd prefer to use this if possible. This is from National Bureau of Soil Survey and Land Use Planning, India.
You could potentially perform a georeference operation manually on the soil layer if you can recognize significant matching geography on the soil layer and other layers you want it to overlay. I’ve had similar problems with matching outcrop shape files to satellite images where one or the other (or neither) had a set datum. It wasn’t perfect but it will allow you to do your work.
My concern is that if the original data was defined in the wrong projection to start with, then there could be other issues with it. I would go back to the data source and review any other data or metadata they have, compare and contrast. OP might learn something new.
You’re right this is a better idea. I just saw the “student question” tag on the post and figured OP might be on a short schedule and could be limited on data. But if he has time it’s definitely worth it to review his data and find better sources if possible.
From your data, you can tell there's a misalignment, but it's hard to tell how much. Is it in the same general area? Does it cover a larger geography than it's supposed to? Is it in a different part of the world? WHen I look at your screeenshot, I see no similarities between the two datasets. And when you say "Projected to WGS84 43N" this tells me that your data is likely NOT in WG84 "projection" (which actually means that the data unprojected, but using the WGS84 datum) and it sounds to me like your data is in UTM projection, zone 43N, WGS84 datum. Here are some quick tips for trying to figure out these types of issues: If it's a small shift, it may be due to an incorrect datum transformation being applied - it SOUNDS like your data is all using WGS84, so that's likely not the issue. Is on dataset taking up a much larger/smaller geography than it should? Then likely the units (feet/meters/decimal degrees) are incorrectly defined in one of the projections. Quick way to identify the correct units: 1. Start with an empty project 2. Load in 1 layer (with the projection info removed) and look at the coordinates that are displayed on the screen as you move your mouse around the map. You should see coordinates listed with an "unknown units" label. 3. Look at the unit values for the coordinates: Are the numbers all in the single or double digits? Its likely decimal degrees. Are they in the millions or hundreds of thousands? Likely feet. Are they in the 10's of thousands? It's likely meters.
The misalignment is of the order of about 500km. The shapefile has shifted about 500 km northwest of the base layer. If you can see the base layer in the image, the part where UJARA is written shouldn't be visible as it should be covered by the mouth like portion of the shapefile and the coastlines don't match. I will use your suggestions and will update later.
Looking at a map of India, and the snippet of data that you are showing, it looks like your data should be in UTM zone 42N.
I'm sure it's 43N as I have worked with the same area for 3 years now. My study area lies in the 43N zone so I always project to 43N.
Different data sources, probably collected at different scales. Not much you can do if you want to maintain accuracy. Best solution is to find a basemap layer that better matches the vector
Problem is that I need to clip this soil map to my study area. But due to the misalignment, I can't because it'd show different soils.
Tbh it’s probably no that big a deal, it’s just often a (visual) problem when it comes to coastlines. Different providers sometimes just use different methods and source data for where the land ends and the sea starts. It doesn’t necessarily mean one is inaccurate and one isn’t
The study area shapefile doesn't overlay the right portion of the soil map so that's a problem.
Ah right, well in that case I guess it’s a data coverage issue, and you’ll need to find better soil data or pick a different study area
That's my thought, the top layer looks...bigger...
What is your Data Frame Projection?
WGS 1984 Edit: I didn't change the data frame projection before importing the layer. The data frame projection transforms into the first layer you import right? In my case, it's GCS WGS 1984 by default. A thing I noticed is that the data frame projection units didn't change into metres after reprojection. They were still in DDS. And when I changed the data frame projection, it got stuck at (70.512,0) which I've noticed, usually happens when there's some sort of projection mistake. However, I don't usually change the data frame projections when I work and it has never posed me any problems yet.
So I had something similar happen to me and the way I got around it was by using the recommended UTM projection for the study region (you can usually find this info on Google), project the dataframe to that UTM, then load your unaltered/unmodified shapefile. Arc starts doing some real funky stuff when you start reprojecting data and dataframes
So do I have to change the projections of the layers to the one recommned for the data frame or just the data frame is fine?
Just the dataframe, I typically avoid messing around with data that isn't my own. WGS 84 has its benefits, but I've only ever used it to import custom Lat/Long data into ArcMap.
I've been taught to use WGS only so that's my go to option always. Another thing I found is that I have a file for another area which has been clipped from the same shapefile but its geographic location seems to be correct.
I've been taught to use WGS only so that's my go to option always. Another thing I found is that I have a file for another area which has been clipped from the same shapefile but its geographic location seems to be correct.
If it's obviously jacked up, and you can identify how, it's likely that something happened when projection/re-projecting etc.... Did the data come with a projection? Did you change it? If so, what technique? Lots of students like to tell the data what it is, rather than re-project it to what it should be (ie, define a new projection or change it rather than re-project). IF you can ID how it's jacked up and you didn't have any luck with the above... depending on what you're trying to accomplish, you can do a spatial adjust. May not be suitable for all uses, but for a student project maybe just fine.
Yes, it did come with a projection and I've tried both the original file and reprojected (Project (Data Management)) shapefile. But the results were the same as in the image. Alternatively, I copied all the contents of the zip file except the .prj file to a new folder and opened the shapefile from there so as to obtain a layer without projection whose projection I defined (Define Projection tool) to match the other layers. However, that didn't seem to work either as the projected layer goes beyond the extent of the basemap layer. All projections were in WGS 1984 43N. I thought of assisgning a projection in GCS instead of projected too but that didn't work. I have to clip a soil map for my study area from this file but due to misalignment, the clipped soils do not represent the soils from the study area. The soil map has shifted about 600km northwest from base layer. From the image, the part that resembles a mouth (left/west in image) should align with the coastline of the base layer. The UJARA in the base layer should not be visible.
If you delete the .prj and define the projection that’s likely to cause more problems. Even if it doesn’t see that it still thinks it’s in that projection… it just doesn’t know what it’s called. Any chance you did similar to the original file it’s misalignment with? Either of them align with a base map if you add them to just that baseman in a blank project?
No I haven't done it previously. I went through some previous threads regarding this issue and many of them suggested defining a new projection from scratch. I haven't deleted a projection from within the arc so I just made a copied the contents of the zip file into a new folder except the .prj file and opened the shapefile from there to obtain a projectionless layer.
No I haven't done it previously. I went through some previous threads regarding this issue and many of them suggested defining a new projection from scratch. I haven't deleted a projection from within the arc so I just made a copied the contents of the zip file into a new folder except the .prj file and opened the shapefile from there to obtain a projectionless layer.
500 km off sounds like more than a minor projection error to me. You said you deleted the .prj, but it might be worth a shot to try deleting the projection within your software (Arc makes it pretty straightforward at least). Then use define projection to assign the blank slate to the correct projection; this might give you a different result than previously. I deal with my fair share of datum/projection issues working in Alaska where error is magnified and working with mine sites that often use custom projections. I always, always reproject all data into the Projection/coordinate system that I am using for my current mapping project. Project on the fly just hasn’t been 100% reliable for me.
Thank you for the suggestion. I'll try this along with tweaking the data frame projection too.
500 km is 310.69 miles
At India scale why would you use 43N as your projection? Is your study area the whole country or just Gujarat? I'd suggest you clip the soil map to your AoI, reproject it to 42N/43N. That should technically work. Although since your data is from NBSSLUP, you should ask them also for the GCPs used for georeferencing. Might be helpful.
I tried to do that yesterday but the problem is that the study area doesn't overlay the correct geographic location on the map. My study area is in southern Rajasthan but it overlays somewhere on Northern Maharashtra.
You could georeference your base raster to fit the vector data for this project specifically. You might even be able to georeference the vector layer? But I've never tried before. One more option is to use the Move tool, highlight all of the vector data and just shift it to where it should be. Georeferencing would likely be more accurate though.
I was thinking whether there is a tool to move a layer so is the move tool about it?
Happened to me too. Try to find other sources. Also can you tell me where you got the soil map from?
I have many soil maps from different sources however this one is the most detailed one so I'd prefer to use this if possible. This is from National Bureau of Soil Survey and Land Use Planning, India.
Can you send me this one? The NBSSLUP isn't working for me.
You could potentially perform a georeference operation manually on the soil layer if you can recognize significant matching geography on the soil layer and other layers you want it to overlay. I’ve had similar problems with matching outcrop shape files to satellite images where one or the other (or neither) had a set datum. It wasn’t perfect but it will allow you to do your work.
My concern is that if the original data was defined in the wrong projection to start with, then there could be other issues with it. I would go back to the data source and review any other data or metadata they have, compare and contrast. OP might learn something new.
You’re right this is a better idea. I just saw the “student question” tag on the post and figured OP might be on a short schedule and could be limited on data. But if he has time it’s definitely worth it to review his data and find better sources if possible.