Shapefile displaced to south pole

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01-19-2015 09:39 AM
BenjaminHerrmann
New Contributor II

Hello community,

I am a Geography student and very new to ArcGIS. Back in August I started a project which asked of me as one of the project tasks to map some paleorivers in Bolivia. So I got into ArcGIS a little and started the work. That worked pretty well and decided to work on other project tasks before continuing my GIS work. When I opened up my ArcGIS project again last week the features I created back then were all moved south of the south pole. Let's look at some screenshots.

world view.PNG

This is where the rivers and the reference image both map: south of the south pole (where the red cross with the "3" are)

basemap zoomed to desired area.PNG

This is a zoom on the desired area. Clearly, there are no lines shaped here.

zoom to layer unspecified rivers.PNG

Those are the lines I drew back in August. They match some paleoriver beds in the map above, but are not shown on the map any more. Look at the display scale, it reads "1 : 0,44" which means that they are displayed smaller than the feature in real life. Of course, this is rubbish, as the displays scale in the first image is 1:40'000.

coordinate system.PNG

When I right-click on "Layers" and go to "Properties" and then "Source" everything seems correct. UTM Zone 19S is the required projection within which I was asked to work. I shouldn't change that.

When I started in August, I opened ArcMap and opened the basemap layer, set the coordinate system of the "Layers" to UTM 19S and found some tutorial on creating a shapefile from scratch, which I followed and image 2 was the result so far, only that it was showing at the correct location back then.

I don't really need any basemap that is provided in ArcGIS, though. The work I am doing requires me essentially to import an image into ArcMap, georeference that image in the right coordinate system, and then map the rivers on that image.

Since that image is not any different from the utilised basemap so far, it would still be nice to know what went wrong.

Here's more:

This is what I obtain from a right click on "unspecified_rivers" > "Properties" > "Source"

Data SourceValue

Data Type:

Shapefile Feature Class
Shapefile:D:\GIS_maps\San_Borja_RF\unspecified_rivers.shp
Geometry Type:Line
Coordinates have Z values:No
Coordinates have measures:No
Projected Coordinate System:WGS_1984_UTM_Zone_19S
Projection:Transverse_Mercator
False_Easting:500000,00000000
False_Northing:10000000,00000000
Central_Meridian:-69,00000000
Scale_Factor:0,99960000
Latitude_Of_Origin:0,00000000
Linear Unit:Meter
Geographic Coordinate System:GCS_WGS_1984
Datum:D_WGS_1984
Prime Meridian:Greenwich
Angular Unit:Degree

Following an image on the image I should use:

zoom to layer imported map.PNG

I georeferenced some points by right-clicking on the crosshairs and then putting in the X and Y-values I got from this Image:

google earth zoomed to desired area.PNG

You can see on this image, that we are in the sector "19 L" at 743 km East and 8362 km South. Now, what I noticed is that as the longitudinal information may be correct, the latitudinal is measured from the South Pole, or more exactly 2000m south of the South Pole, because as you travel south, the numbers decrease but never under a value of 2000m.

This is the link table of the control points as I entered them 2 hours ago:

link table of control points.PNG

As you can see, the numbers match those in the Google Earth image and I entered the Y-coordinate with the negative algebraic sign, because I thought it measured from the equator. Still, I tried to flip the minus to positive in the link table and the reference image didn't really move anywhere north of the South Pole.

Just ask, if you need any more information. In the meantime, I will start over and this time start with the reference image and then draw the lines.

I am excited to see your answers. Please promote this thread to anyone you think might know what mistakes I made while working on this project. You may, of course, also only answer to one of the presented problems. Any insight is appreciated.

Cheers,

Benny

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Accepted Solutions
ToddBlanchette
Occasional Contributor II

Hi Benjamin,

Much like Melita said, it appears your shapefile was created using a lat/long coordinate system (GCS), but it is trying to present itself as a UTM projection now.  I've seen this happen when people use the "Define Projection" tool incorrectly.  All the tool does is setup whatever projection metadata you give it into the .prj definition (you CAN give it the wrong information, hence errors).  If you run the "Define Projection" tool and set it as GCS_WGS84, your shapefile should now draw at the proper location in Lat/Long.  If you wish to transform the shapefile into UTM 19S afterwards, use the "Project" tool, which will create a new shapefile with the same data, but in the new source projection.  This is recommended if you're going to be doing any measurements on the data later on.

Hope this clarifies things!

Todd

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11 Replies
XanderBakker
Esri Esteemed Contributor

Hi Benjamin,

First of all, congratulation on the detailed description you provided (this must be ne of the largest I've seen). There are a few things I notice:

In the zoomed in image (# 3 with the selected lines) I notice the scale value (1:0,44) and the coordinates in the lower right corner (95,305 8,899433e+015 Decimal Degrees). Also other images present geografic coordinate outside the range of -180 to +180 (longitud) and -90 to +90 (latitud).

Although your coordinate system of your data frame might be WGS_1984_UTM_Zone_19S, it seems that they may be interpreted as decimal degrees.

In the georeferencing window I notice the X Map and Y Map coordinates to be te small. The comma is a decimal while the coordinates plotter in the Google Eartch screem dump seem to be a factor 1000 higher. Please re-enter the coordinates in the columns X Map and Y Map or edit the existing ones, and make sure that the correct coordinate system is used.

Maybe something happened with the definition of you decimal symbol (point or comma) on your system in the mean time...

MelitaKennedy
Esri Notable Contributor

I'm having trouble reading through your entire post--I'm going to blame the cold that I'm fighting, and the time of day (late in the afternoon). UTM South zones have a false northing at the equator of 10 000 000 meters. So the origin of the Y/northing values is near the south pole. Thus +8 000 000 m for Bolivia which is around 20 degree South is correct.

Beyond posting the coordinate system details of your data, could you post the extents? You may need to deal with the data in separate ArcMap sessions to make sure that they're not being projected on-the-fly.

Beyond Xander's note that the data could be in decimal degrees, another possibility is that the data is in a UTM North (N) rather than South (S) zone. That would give you around -2 000 000 m for the Y/northing values.

Melita

BenjaminHerrmann
New Contributor II

thanks Xander Bakker‌ and Melita Kennedy‌. I will look into it next week and communicate my findings. Just by reading the answers I can't say if I will be able to get Arc to work the way I want it, but I'll try.

Melita, to put it shortly, here's what I want to do:

  1. open a blank project.
  2. set the layers coordinate system to UTM_Zone_19S
  3. import an aerial photo
  4. define anchor points and read out the coordinates of those (can I do that with G-Earth when using it with UTM coordinates?)
  5. georeference that photo with anchor points
  6. create a new shapefile with line features (I have to look that up again, I don't remember how I proceeded the first time I did it)
  7. draw those line features (they're gonna be meandering paleo-river beds)
  8. measure the radiuses of the drawn lines

(The basemap is not required, but I will eventually load it to see if the imported image was georeferenced correctly. In the end, I will need to have the coordinate system draw around my map and it would be nice if those coordinates were the right ones)

Cheers,

Benny

PS: I attached a file which shows the extent of the unspecified_rivers shapefile

layer properties - source - of unspecified rivers.PNG

That is a rather negative extent. What have I done? Have I pushed my rivers of the edge of the world?

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MelitaKennedy
Esri Notable Contributor

Ah! The shapefile is in latitude and longitude aka a geographic coordinate reference system. Change its coordinate system to WGS84 and see if it lines up. If not, try PSAD 1956 (under geographic coordinate systems, South America). If using the latter one, you'll also have to set a transformation, PSAD_1956_To_WGS_1984_2, in ArcMap (see the Transformations button on the Coordinate Systems tab in data frame properties.

Melita

BenjaminHerrmann
New Contributor II

Melita Kennedy,  I see what you mean (do you get a notification I answered on your comment without the @-mention?). The -14,xxx m are actually 14,xxx°S and respectively 66°E. Both values are in meters. But the projected coordinate system is already WGS_1984_UTM_Zone_19S and the projection transverse Mercator. How am I to change the CS to WGS84 when I appears to already be in that CS?

From what you wrote, I understand that the extent of the shapefile is not consistent with the CS (or Projection or Projected CS, for that matter; I still have difficulties distinguishing between those three. I have to look that up.), I still struggle to understand how I should proceed.

Should I not rather manually reset the extent of the the shapefile? Is that even possible? Do I need to use the "Spacial Adjustment" tool? Or should I change the coordinate system like you wrote?

I'm sorry for the lot of questions, I'm a bit lost.

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MelitaKennedy
Esri Notable Contributor

Hi Benjamin,

I think I would get a notice, because once I reply to a thread, I'm now "following" it (I think!), so even if I didn't get an email, I would see a notice in my inbox/activity area when I logged in next time.

The coordinate system information is just metadata that describes how to interpret the coordinate values. Right now, the metadata is incorrect. It says that the coordinate values are UTM, but they're not. These very small values (when interpreted as UTM) place them near the South Pole!

So, in ArcCatalog or using the Define Projection tool, change the metadata to be a geographic coordinate system and the coordinate values will make more sense.

Hope this helps!

Melita

ToddBlanchette
Occasional Contributor II

Hi Benjamin,

Much like Melita said, it appears your shapefile was created using a lat/long coordinate system (GCS), but it is trying to present itself as a UTM projection now.  I've seen this happen when people use the "Define Projection" tool incorrectly.  All the tool does is setup whatever projection metadata you give it into the .prj definition (you CAN give it the wrong information, hence errors).  If you run the "Define Projection" tool and set it as GCS_WGS84, your shapefile should now draw at the proper location in Lat/Long.  If you wish to transform the shapefile into UTM 19S afterwards, use the "Project" tool, which will create a new shapefile with the same data, but in the new source projection.  This is recommended if you're going to be doing any measurements on the data later on.

Hope this clarifies things!

Todd

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BenjaminHerrmann
New Contributor II

Ultimately, this is what I need to do. I need the data to be projected in UTM 19S and do measurements. Thank you very much for helping with this.

Melita Kennedy‌, Xander Bakker‌, Todd Blanchette‌, all of you helped me very much and I would like to thank for this. It's a shame i can't mark more than one answer as the "correct answer". Since Todd, you based your answer on Melita's and she's done her best at understanding my predicament, I gave her the credit for it. I think you'll agree.

Best and thanks again,

Benny

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MelitaKennedy
Esri Notable Contributor

Because answering GeoNet equations could be considered part of my 'job,' feel free to mark Todd answer as the correct one instead!