topic Overlaying in Data Management Questions

Overlaying

alexandernongkhlaw — Wed, 15 Feb 2017 12:18:50 GMT

Hi please help me it is very urgent...i have a vector data of 1:25000 which was digitized and the raster is of 1:50000...so now i wan the vector data to aligned with the toposheet of 1:50000 as their is a shift when i overlay the vector data on 1:50000 toposheet..how can it be done so that the vector data is aligned on 1:50000 toposheet..please help me..thank youw

Re: Overlaying

NeilAyres — Wed, 15 Feb 2017 12:56:28 GMT

How far is the shift?

They will always be differences if these 2 datasets are from different sources and scales.

Coordinate system? Datum shift?

Re: Overlaying

DanPatterson_Retired — Wed, 15 Feb 2017 13:44:12 GMT

right-click on each layer and examine its properties, the coordinate system specifically and the datum in particular. If the datums are different, (ie NAD27 vs NAD83) then you need to use the Project tool to project one to the other. If one doesn't have a defined coordinate system (ie it is undefined) you had better find out what it is, then use the Define Projection tool prior to using the Project tool if needed.

Re: Overlaying

JayantaPoddar — Wed, 15 Feb 2017 13:50:08 GMT

Considering both the vector data and the toposheet are in same coordinate system,

1) If the shift is uniform, you may like to select all features and use Move tool from Editor Toolbar Moving a feature by dragging it

2) If the shift is non-uniform, you may like to use Spatial Adjustment toolbar. About Spatial Adjustment

Re: Overlaying

alexandernongkhlaw — Thu, 16 Feb 2017 08:30:20 GMT

Yes they we're digitized of different scales the vector data is of difeerent scale its of 1:25000 wheras i have a toposheet of 1:50000 so i want to know if i can do anything with it or not...since the drainage and roads are shifting even though i overlay on google earth...so is there a way to correct the data..

Re: Overlaying

alexandernongkhlaw — Thu, 16 Feb 2017 08:34:06 GMT

both the data are of correct projection...but the shift is still there even for drainage and the roads....even when i overlay on google earth the shift is still there...

Re: Overlaying

DanPatterson_Retired — Thu, 16 Feb 2017 10:18:28 GMT

Just because a coordinate system is defined, doesn't mean it is defined correctly a consistent shift is generally an indicator of an inappropriate use of the Define Projection tool at some stage of the history of the file particularly if the shift is consistent within the map and ... for some area... in the 100s of meters.

Can you provide some values for the shift? Whether the shift is the same in all cardinal directions? Also note, that maps digitized from sources at different scales won't align exactly because of errors during the digitizing process.

Re: Overlaying

alexandernongkhlaw — Thu, 16 Feb 2017 10:26:36 GMT

its around 200m...few are 100 m...300 m shift.....the vector data we're digitized at a scale of 1:25000 and i have a toposheet of 1:50000 so i wan to overlay it in 1:50000 so is there any method wer i can align them at 1:50000

Re: Overlaying

NeilAyres — Thu, 16 Feb 2017 14:37:53 GMT

If it was all around 200-300m I would definitely point to a datum difference between the 2 datasets.

Have you tried overlaying the data on top of some of the online basemaps like imagery or something?

What do you see in terms of alignment?

Re: Overlaying

alexandernongkhlaw — Fri, 17 Feb 2017 11:45:48 GMT

ive tried on google earth the shift is still there ..n even on geoeye of 5 m resolutions there's still a shift...what to do???

Re: Overlaying

DanPatterson_Retired — Fri, 17 Feb 2017 12:35:47 GMT

show an image of what you are talking about, it could be you are just trying to reference bad digitizing if there is no pattern to the problem

Re: Overlaying

alexandernongkhlaw — Fri, 17 Feb 2017 12:48:01 GMT

Re: Overlaying

DanPatterson_Retired — Fri, 17 Feb 2017 12:55:27 GMT

How were these created? was CAD involved? they look slightly rotated and scaled. This isn't just a coordinate system issue and I doubt they will ever match perfectly or even close since, although there are similarities, the differences between them is great. I would pick the one that matches the imagery ... if one does ... and use it. If the digitizing was done of the image, its coordinate system would need to be known in the event that the coordinate system of the vectors used it

Re: Overlaying

alexandernongkhlaw — Fri, 17 Feb 2017 13:00:09 GMT

the green line was digitized of different scale i guess cause i just got the data from a friend whereas the red line s from field survey so inorder to save time i ask from my friend since all the data s there so i dont need to go to the field anymore

Re: Overlaying

alexandernongkhlaw — Fri, 17 Feb 2017 13:01:07 GMT

so thats why i wana know if theres any method to get the data correct

Re: Overlaying

DanPatterson_Retired — Fri, 17 Feb 2017 13:09:46 GMT

trying to use spatial adjustment but I suspect that the number of links needed between the two may be too many and the results less than satisfactory. You could give it a try, or if you are just trying to show additions or removals or small changes in the network, it might be faster to just do those to a copy of the 'best' one that you have. Give it a try first

Re: Overlaying

alexandernongkhlaw — Fri, 17 Feb 2017 13:12:26 GMT

ok il try..thank you