Geolocation Map Coordinates Doesn't Match Google Earth Coordinates

[Anonymous]

Hi,

I have Autocad 2016. I am trying to use georeference a drawing using the Set Location feature and

I want that it matches with Google Earth coordinate system.

This are the steps that I'm following:

1- Get the lat/lon of a reference point (42.539081 / -70.941904) in Google Earth.

2- In Autocad click Insert>Set Location and drop a pin at the above point. When I

do that the map show the same point as in Google Earth.

3- I click "Next" and select a Coordinate System (WORLD-MERCATOR / WGS84 / Meter).

I leave the drawing units in meters.

4- I select a point in the drawing that correspond to the reference point in Google Earth

and use ortho to indicate the north direction.

Then Autocad places a Marker on the drawing and the map that appears below. A visual

check of the location of the Marker on the map in Autocad and Google Earth shows that

it's the same location. The problem comes when I compare the coordinates in Autocad

vs the coordinates in Google Earth, (340132 E, 471248 N) vs (340538 E, 4711460 N) respectively.

What I'm doing wrong? Here are some images:

[imadHabash]

Hi,

i suggest to assign geographic location using online maps service and after signing in to Autodesk 360 .  >> Click <<

OR you can from Autodesk App Store to get >>  CAD-Earth << which designed to easily import and export Google Earth images.

regards,

[ChicagoLooper]

I would recommend a projection using Massachusetts State Plane, specifically Massachusetts Mainland (US-feet), EPSG 2249. If you want to match Google Earth's projection, then I'd recommend the WGS ellipsoid  referenced to UTM84 zone 19north (meters). 

The reason they don't match is because the easting and northing coordinates shown in your Google image is referenced to UTM (Universal Transverse Mercator) zone 19 and the coordinates shown in the Cad image, the numbers at the bottom, are referenced to an arbitrary spot that you clicked with your mouse. Review your workflow and you'll see that in step 4 you instructed Cad to put the pin (the Bing Imagery) at the location of your mouse click. Cad has indeed forced that 'clicked spot' to correspond to the lat/long of your pin, but it won't necessarily force your clicked spot to correspond to UTM meters shown in the Google image (it forced the x-meters and y-meters to your clicked spot, not the true easting/northing). Instinct tells us it should match, but it doesn't. 

Cad prefers this sequence:

1. A projected coordinate system.
2. A geographic coordinate system.

But your workflow is doing this:

1. Geographic lat/long's you entered in step 1.
2. Projected UTMs of easting and northing in step 4 which you created from your mouse click . 

The workflow is going backwards and Cad simply doesn't have enough info to do it in reverse. Review your workflow. Is UTM-zone 19 ever mentioned? Cad knows lat/long but he doesn't know you need UTM-19 easting and northing.

To make this work for you, open a blank template and do this:

1. Assign Massachusetts State Plane MA83F (US feet), EPSG 2249, using an Imperial template. Alternatively, use UTM84-19N (meters), EPSG 32619, using a metric template.
2. Go to Geolocation tab=>Tools panel=>Mark Position icon=>then choose Lat-Long from button's dropdown
3. Type in latitude, enter.
4. Type in longitude, enter. (Don't forget "-" sign)
5. Type SITE for the label, then click an empty area in modelspace to end command (don't hit enter). Select that newly created marker and make it bigger by increasing size in Properties Palette. Change it from 1 to 50.
6. Click the marker and view Position X and Y in geometry section of properties. Is it correct?
7. With marker still selected, scroll to bottom of properties and view lat/long in location section. Is it correct?
8. Turn on Bing maps.

Notes:

• It doesn't matter whether you use imperial-feet or metric-meters template. Lat/long is same either way.
• If lat/long in #7 above is deg-min-sec, then enter LATLONGFORMAT and change it to "0" for decimal degrees.

[Anonymous]

Hi,

Thank you for your answer. Maybe I didn't show all the picture of all the steps that I followed,

but I used Insert>>Set Location>>From Map; like you suggested.

I think that at first my problem was that I was using an arbitrary spot as reference, like ChicagoLooper mentioned

in his answer.

But, even after correcting that step I still don't get a good match with Google Earth in different test points.

Check my answer to ChicagoLooper for more details.

[Anonymous]

Hi ChicagoLooper,

Thanks for your reply.

I made the correction in the steps that you suggested but I still don't get a good match in different points around

the reference marker.

I need the match between Google Earth and Autocad because I have 3 thousand points that were capture

with a GPS receiver that match almost perfectly with Google Earth, and I have to insert blocks at those

points on the Autocad drawing. For this I'm planing to use a script.

First these pictures show the steps I took:

Now the comparison between several test point in Autocad and Google Earth. The red pin in Google Earth is the

Autocad's coordinate and the yellow pin is Google Earth's coordinate for the same location. The weird thing is that

when change Autocad to show Lat/Lon values and used those values in Google Earth all the test location almost

match perfectly.

[TerryDotson]

...3 thousand points ... GPS receiver ... insert blocks ... use a script.

Can you zip and post your point ascii file (assumed to be lat/long)?

[ChicagoLooper]

The difference between Google Earth locations vs. Cad locations looks like it is due to not enough decimal places when you enter the lat/longs. For accuracy, use 6 decimals, no less. Also your drawing should display 6 decimals for meters--you attached images only show 4 and you need to fix that.

Your workflow is highly questionable. You are using Map 3D (or Civil 3D) and you are inserting blocks which represent 3,000+ points. You should simply insert points to represent points, not blocks. I can only think of two reasons you would use blocks: if you need to use the block attributes for labels or if you need to perform data extraction on the blocks once they're inserted.

If you still want to use blocks and not points, it still can be done of course without using a scrip because Map 3D will insert the blocks for you, it's just simpler to insert points especially when you don't need to label the blocks. You wouldn't use a script that I wrote, or anyone else wrote to draw a circle, would you? I think you'd rather use the built in circle command. Likewise, why would you use a script to insert a list of points when Map 3D has a built in function to do it for you?

To get the points to be consistent with Google Earth, you must disclose more info or upload your list, or partial 10% list, of the points you wish to insert. By uploading, you will reveal your points, I.e. whether you start with lat/longs or northing/easting, whether your point list is .xlsx or .csv format, whether your data has 4 or 6 decimal places, whether you need point numbers to match the point, whether you really need a block or can a point will suffice, whether the points are spread out or clustered together, hence the reason to use points instead of blocks because if clustered together the blocks will touch and blend together and end up looking like a super big blob when you're zoomed out.

[ChicagoLooper]

Your points, the 5 you have used in you attachments, are inserted and shown in the image below. No script was used. Units for insertion were the UTM-meters and not lat/longs because you only provided lat/long for point 1 and not for the other four. The best part is even though UTM-meters were used to insert the points, the drawing itself has the assigned coordinate system of Massachusetts State Plane, Mainland, US survey feet (no it doesn't use WGS84 UTM-19N meters). Contrary to popular belief, you do NOT need to assign a coordinate system to your drawing that matches the coordinate system of your points because Map 3D will, on it's own, without a script, perform a transformation from Google's WGS84 UTM-meters to State Plane MA83F for you. No script used for coordinate transformation either, all through Map 3D.

Five points inserted without using a script.

[Anonymous]

Hi ChicagoLooper,

Thank you for the attention and the answers. I'll try to answer both of them here, but first let me give you more information about the tools and data that I have, and what I'm trying to do:

        * Tools : Autocad 2016, Google Earth, Google Map, and Excel. I don't have Map 3D or Civil 3D, and I have never    used those programs.

        * Data: I have and Excel file Lat/Lon (with 8 digits after the decimal point) and other data for pole locations. Here is a picture of the file and also with the link you can get a subset of the data (200 points):

https://drive.google.com/file/d/1iA2TY4onQtwqFZ5NjoGEVfaEopV5giCm/view?usp=sharing

      Also I have a dwg drawing of the city of Peabody (not georeferenced) shown in the picture below, that is the same you can see on this link: https://peabodyma.mapgeo.io/?latlng=42.532644%2C-70.973657&zoom=13

       * Goal: I need to plot the location of 9 thousand poles on the dwg file using the information (Lat/Lon) from the excel file. The poles should be represented as circles and have attributes, that's why I want to use blocks.

         I plotted the poles in Google Earth and I got points with pretty good accurate for my purpose, as you can see below.

         My idea to accomplish this has being:

      1- Use Autocad>>Set Location>>From Map to georeference the dwg drawing and make it match Google Earth coordinate system.

      2- Convert the Lat/Lon to UTM values and use those UTM's values to plot points in the georeference dwg drawing.

      3- Use a script to insert blocks at the plotted points with attributes from the Excel file.

      4- Use the projected bing map that Autocad places under the dwg drawing to draw some missing street and buildings

  Is it possible to do this with Autocad 2016 alone, or do I need Map 3D or Civil 3D? Is the georeference done with Autocad>>Set Location>>From Map a good method?

Now to answer some of your recommendations:

   * I used Lat/Lon with 6 decimal place to set the location of the marker in Autocad>>Set Location>>From Map window and I got the Lat/Lon for that point from Google Earth. So, I don't think that the problem that is causing the mismatch in the points is due to lack of precision in the Lat/Lon used for the marker.

   * I increased the precision of the units in Autocad but that didn't improved the big difference when I plotted the Autocad's UTM coordinates for the test point in Google Earth.

   * I still don't understand why when I change the coordinates in Autocad from UTM to Lat/Lon and I use the Lat/Lon of the test points in Google Earth I get almost a perfect match. It looks like the convertion from Lat/Lon to UTM that Autocad is making creates the difference. I don't know if I can input Lat/Lon in Autocad insted of UTM values.

  * In the test that you did with the 5 points using Map 3D did you try to plot those points in Google Earth using the UTM values from Map 3D? Did they matched?

Thanks for you attention.

Poles in Google Earth

[ChicagoLooper]

Thank you for the full disclosure. It looks like you don't have the right tools to do the job. You probably should send it to someone who does, like someone in the engineering department who has either Civil 3D or Map 3D. Or you can send it to someone in GIS. Plain vanilla CAD doesn't have the geospatial capability nor the ability to deal with tabular data.

If it was me, I'd use Map 3D. I would first create a shapefile to represent the poles. I'd use the exact same file you uploaded since it has the lat/longs and the data tabulated. Once the shapefile is created it could be used 'as is' and brought into Cad through FDO connection. The shapefile could also be imported to Cad. If it were imported, then blocks would represent the poles and object data would be generated from the shapefile's attributes. Deciding whether to use a shapefile or block would depend on the requirements of the final presentation as well as the type of query run to produce the final deliverable. A combination of both can also be powerful when drawing the final map.

The key to this entire exercise is to leverage the data that someone else, or some other department, has already gathered and tabulated. You are merely taking the spreadsheet and presenting it in a visual map form.

As an alternative to Cad, you may perform the entire exercise in Google Earth Pro. First, re-save your spreadsheet. For demo purposes, use the same file you uploaded, to a csv (comma delimited)*.csv. (Do not attempt to modify or edit the file.) Then, open GE Pro and do this:

1. From GE Pro, go to File>Import>your newly saved csv file
2. In Specify Delimiter, For Field type choose Delimited. And for Delimited choose Comma. Then click Next.
3. In Select  Latitude/Longitude Fields = keep all default values. Next.
4. In Specify Field Types = keep all default values. Finish.
5. Do you want to apply a style template? YES.
6. Create new template. OK.
7. In Style Template Settings, Name tab, Set Name Field = Select Pole_Number from dropdown. OK.
8. Save. (Don't change the folder, save the template in default location.)
9. Back in GE Pro, Places Panel on left, scroll to bottom of the Places Panel and check the box for your imported csv file.
10. To customize the points, right click the import file in the Places Panel and select Properties.
11. In Style, Color tab, click 'Share Style'
12. Click icon button to the right of 'Name' and select a symbol (leave color and scale as-is) OK.
13. In Icon section, change color by clicking on color swatch. Change scale for icon to 1.0. OK. 
14. To save your points for future use, right clIck your point layer in the Places Panel and perform a save as. Be sure to remember the saving folder.

Note: The points you just imported are temporary. If you don't save them, they won't appear the next time you open GE Pro and you'll have to perform the import all over again.

[ChicagoLooper · Accepted solution]

Unfortunately, you are not using the 'Geolocation Tool' correctly. (OP shown below.)

It's imposrtant to know which Coord. Sys. to use.

Using Map 3D, Geolocation Tab>Tools panel>Mark Position Icon>Choose Lat-Long from dropdown you have the ability to place a geomarker (cyan). Note: Decimal places for Position X & Y and Lat/Long have 6-significant figures. If you switch GE Pro to display UTMs, then the appropriate projection in your drawing is UTM84-19N, meters (84 means referenced to WGS84 and 19N means zone 19 northern hemisphere.)

Using UTM84-19N, properties show (x,y) and Lat/Long.

[Anonymous]

Hi,

I was able to use Map 3D to assign a coordinate system ( UTM84-19N) and align the drawing using two points of reference and now it matches with Google Earth and aligns almost perfectly with the Bing Map in Autocad, as you can see from the picture below.

I don't understand why it worked with Map 3D and not with Vanilla Autocad, since I used the same coordinate system (UTM84-19N) when using Geografic Location, like I showed in previous replies.

Since I am new to Map 3D, I'm not sure how to create the shapefile that you mentioned. My guess is that the entities (polygons, polylines, etc) in the drawing should have some king of ID to be able to connect then to an external database or excel file with a column with the same ID.

I don't know if Map 3D has a function where you give it the coordinates of multiple points and it automatically plot a shape (circle or polygon) at those locations. For the future use of this map, I should be able add other elements like transformers, capacitor banks, switches, wire, etc; which also have a set of attributes. The poles will be the reference to trace the distribution circuits.

Regarding plotting the poles on Google Earth Pro, I already did, but it doesn't have the flexibility that Map 3D has.

Thanks.