Latest Contributions by SimonKettle

The operator from Kalianpur 1937 datum to WGS84 datum is Kalianpur 1937 to WGS 84 (1) (epsg 1155). The process to transform from Kalianpur 1937 to WGS84 datum is use the Project tool in ArcGIS Desktop and assign the appropriate parameters in the tool. As mentioned by Dan Patterson‌ you can look up the available transformations in this ESRI doc. FYI the following applies: Kalianpur 1937 to WGS84 (1) is a Geocentric Translation with the following variables dx: 282 dy: 726 dz: 254 ... View more

As Melita Kennedy‌ suggested in her comment to find a list of appropriate coordinate systems use the coordinate system filter from the Data Frame properties. Do this by: Zoom to your AOI Right click Data Frame select Properties select Coordinate system tab On the left hand side of the text search click the filter and select Set spatial filter This will reduce the number of available coordinate systems for your defined extent. You could also use the IOGP CRS polygons layer available on arcgis.com  ... View more

Hi Lincoln Hood‌ - I have done this analysis before when I was working in the maritime industry. So, let's break down your question as there's several items in there: 1. The files .cpg, .dbf, .prj, .shp and .shx which you mention are the components of a shapefile. My first suggestion would be to import those shapefiles into a file geodatabase, it'll work quicker and it's easier to manage. 2. You suggest that you want to filter the data by timestamp and craft_id...this would involve combining all the feature classes (those shapefiles you imported to feature classes in a geodatabase a moment ago) into a single Feature Class (use the Merge tool) this will mean in a single database you will have all records in a single table, perhaps put this Feature Class in another File Geodatabase - you'll potentially end up with a large database but it'll be easier to work with for this analysis. 3. Filtering the database can be added to an ArcMap session as a layer. In layers you can apply definition queries. Use definition queries to filter out your data for example: Craft_ID = 123 AND Time_stamp > 01-01-2012 <=01-01-2019...Using the filtered layer you can run the below tools to end up with outputs for the filtered data. Of course, you could run these tools over the whole dataset but it'll likely take some time. 4. Converting the point data to lines try using the Points to Line tool...and the Craft_ID as the Line Field and the Timestamp for the Sort Field...let me know if that works, you should end up with lines per Craft_ID sorted by Time...this might take some time given considering the quantity of data...with the result you should have an approximate route for the vessel. 5. Once you have the lines you can use Line Density or the Calculate Density tool (you could also use Calculate Density tool with the points directly which might superseded the need for creating lines if the density of points are as required). There are various other density tools which maybe more appropriate like the Kernal Density tool but you'll require the spatial analyst extension for this. It'll probably be easier if you have any questions on the above process to email me: skettle@ggspatial.co.uk  ... View more

Hi gourav panchal‌ and welcome to the Coordinate Reference Systems Place! To determine the accuracy of a DEM requires some "true" elevation values, like point locations you know are accurate so that you can measure the error of a DEM vs the true values. The process would include the following process: Compute the root mean squared error (RMSe) between the DEM elevations and the "true" elevations at your reference point -- the RMSe is the "average error." Produce an error map that presents the RMSe values at each reference point. Use these reference points to create an interpolation (kriging, IDW, etc) to estimate errors at non-reference points. Or a cross validation technique. However, I am not sure if that is the question you are asking. In your example above you explain how you have delineated the boundary of a watershed per DEM. So you should have 4 DEM delineations. You want to know which one of these is the most accurate. Well, I would assume you have calculated these directly from the DEM and therefore the accuracy of the watershed will be dependant on the resolution of the DEM (think 30m is worse because it is coarser than 10m) and the technique used to generate that DEM. For example, ASTER is based on optical data and SRTM is based on radar interferometry (both have a 30m resolution). This has consequences on the surface produced. ASTER is typically noisy in areas of strong topography vs SRTM which can be noisy in areas of low topography. On the other hand Cartosat was compared with SRTM in a paper listed below where it was determined that the higher resolution did not matter much in the generation of a stream profile. Essentially, I think you need to research the most appropriate DEM type based on how it was made as well as its resolution to make an informed decision on which watershed delineation is most appropriate for the question/analysis you are trying to answer. This in my opinion is not about positioning or vertical measurements but rather which is the most appropriate dataset being used on that note I have shared the question with the Analysis and Imagery and Remote Sensing‌ See this Comparison of ASTER to SRTM https://opentopography.org/blog/comparison-aster-gdem-srtm  See this Comparison of Cartosat and SRTM http://technical.cloud-journals.com/index.php/IJARSG/article/download/Tech-480/pdf  ... View more

Can you give an example of the code required to import the MXD file names as Map View names?  ... View more

What were the units that you extracted from Google Earth? (where coordinates in meters/dedimal degrees) It sounds like you added some coordinates from a geographic coordinate system to a projected system where the origin of the projected system is a 0 degree long and 0 degree lat (hence why the points have plotted off West Africa) The following blog might be a good place to start? https://community.esri.com/groups/coordinate-reference-systems/blog/2018/12/12/checklist-adding-coordinate-values-from-a-spreadsheet  ... View more

Thanks for the update Melita Kennedy‌! As you say in the notice ,please keep us informed of any pending changes... ... View more

Now you're back in business have a look at NOAA's vertical datum transformation tool (VDatum). There's information about the tool and more detail on vertical datums in general. NOAA/NOS's VDatum 3.9: Vertical Datums Transformation   ... View more

Hi Chuck, In your first question you mention "I see many engineers using MSL, but I believe, should be using NAVD88 as a vertical datum." I think this blog from this place might be of interest as there's a bunch of ambiguity around MSL etc... https://community.esri.com/groups/coordinate-reference-systems/blog/2014/08/14/mean-sealevel  Regarding the next question: "what [is] the cut-off distance is between use of a tidal gauge and/or NAVD88." With regards to the validity of a tidal gauge reading against distance from that gauge. I would treat the gauge as a single point of reference much like a survey triangulation point but arbitrary and local so maybe not like a survey triangulation point. This is because local variations in sea level are really subject to large hydrodynamic influences especially close to the shore. So, there isn't a rule of thumb as every tidal gauge would have to be seen in the context of it's local situation (e.g. topography, bathymetry, currents, etc...) perhaps a number could be achieved after hydrographic modelling. A rule of thumb would work however, it would be impossible to have a regular assumed error of vertical error based on distance from the gauge. NAVD88 is based upon levelling of height observations across the USA and I understand that a model was built after hurricane Katrina to interpolate height, from local sample locations (i.e. tide gauges) so that an accurate model of MSL along coastal regions could be achieved. There is documentation on this on NOAA's National Geodetic Survey (NGS) but the website is unavailable until the Federal Closure ceases. I hope this helps. ... View more

Sounds like something to add to the list of ideas for ArcGIS Pro. ... View more

Go through the checklist...https://community.esri.com/groups/coordinate-reference-systems/blog/2018/12/12/checklist-adding-coordinate-values-from-a-spreadsheet  Are the values in the CSV angular or linear?  Also show an example of the data...it makes it easier to answer ... View more