Latest Contributions by PeterWilson

‎08-09-2011

I'm currently using ArcGIS 10 SP2 on Windows 7 64bit. I'm working on a very large railway alignment design project and need to generate "Average Catchment Slopes" for each watershed. The problem that I have is that the "Zonal Statistics as Table" tool does not process overlapping polygons. It's mentions in the help that if the polygons overlap, that should be processed interactively to overcome this. I haven't been able to find any supporting documentation to achieve this. Just a note, I have over 600 watersheds that I need to process and a manual process will not be possible if I'm to meet my deadline. Any advice will be appreciated. Regards

‎06-13-2011

I'm looking for the correct workflow to copy an existing model into a new folder and use it as a starting point for another Arc Hydro Model. This is my current workflow: 1: Copy the the following from the previous model: Layers folder; File Geodatabase; and mxd. 2: Paste the items copied from the previous model into a new folder titled "Model2". 3: Repair the Sources of the copied mxd to the new location of the raster and vector layers 4: Set the Target Locations to the new location of the raster and vector data. 5: Delete the records within the following Feature Classes: BatchPoint; Watershed; WatershedPnt; LongestFlowPath; 6: Append the new locations into the BatchPoint Feature Class 7: Run the Batch Watershed Delineation and remainder of the Catchment Characteristics (LongestFlowPath; Centroid; Slope10/85) Is there any other adjustments I need to make to ensure that the new model works correctly? I'm subdividing my study area into multiple Arc Hydro models and trying to eliminate unnecessary work. Regards

‎06-13-2011

Hi Alvaro I have come up with a solution, based on my discussions with Dean Djokic from the Arc Hydro Team. I'll firstly try to explain what I was trying to accomplish. I'm currently working on two railway alignment projects, the one is within Liberia/Guinea which is +/- 760 km in length and the second is within Malawi/Mozambique which is +/- 1000 km in length The engineers have supplied us locations where structures (Bridges/Culverts) are required based on there preliminary assessment using a strip survey +/- 100m on either side on the alignment. We were tasked to determine the hydrology characteristics for each structure as well as identify where additional structures would be required. In order to determine the catchment characteristics (Catchment Area; 10/85 Slope; Length to Centroid; Longest Water Course & Average Slope) for each structure, we used the SRTM 90m DEM. We originally ran the entire terrain preprocessing steps within Arc Hydro and then used a manual approach, using the Trace Flow Path tool which is found within the Arc Hydro toolbar to identify additional flow paths in order to determine where the structures (Bridges/Culverts) should be placed and to calculate the catchment characteristics. This was tedious and very slow. Our new approach involves the following steps 1: Convert Railway Alignment Polyline into a Raster Grid 2: Convert the Railway Alignment Grid into a Point Feature Class 3: Interpolate to shape the FAC (Flow Accumulation Values) based on the location of the points 4: Filter out the points that have a FAC (Flow Accumulation Value) which is 0 or is below a predetermined threshold 5: Load the FAC Points into the BatchPoint Feature Class 6: Generate Watersheds based on the new BatchPoint's 7: Eliminate unnecessary Watersheds based on Visual Inspection 8: Generate the remainder of the Catchment Characteristics for the Watersheds Regards

‎06-07-2011

We are currently designing a new Railway line and need to define where structures are required along the alignment. I have come up with the following workflow and would like to ask for assistance in implementing my workflow. 1: Convert the Railway Alignment into a raster grid (same cell size as flow accumulation grid) What is the best method to convert the railway alignment polyline into a raster grid that has the same cell size and overlays correctly on top of the flow accumulation grid? 2: Use a conditional statement (Map Algebra) to generate a new flow accumulation grid based on the intersection of the flow accumulation grid and railway alignment grid. How would I structure my conditional statement to generate a new flow accumulation grid based on where the two grids intersect if I don't know the range of values beforehand? 3: Use the new flow accumulation grid to define the type and location of structures are required based on the flow accumulation values. (i.e. higher = bridge and lower = culvert) Any advice in developing a criteria based on the flow accumulation value along the railway alignment to define where structures will be required as well as type will be appreciated? Regards

‎06-07-2011

I currently have a 90m Cell Size Flow Accumulation Grid and need to convert a Railway Alignment Polyline into a raster that will match the Flow Accumulation Grid. How do I ensure that the Railway Alignment Grid overlays correctly on top of the Flow Accumulation Grid. I'm trying to generate a new Flow Accumulation Grid based on the intersection of the two grids. Any advice in converting the Railway Alignment Polyline into a Railway Alignment Grid with the lease amount of error will be appreciated. Regards

‎06-07-2011

I looking for some advice in how to construct a conditional statement to generate a New Flow Accumulation Grid where it intersects a Railway Alignment Polyline that I have converted into a raster grid. The problem that I have is that I don't know before hand the range of values that I'll be dealing with and the New Flow Accumulation Grid needs to be the result where the two grids intersect. Any advice to constructing a conditional statement will be appreciated. Regards

‎06-01-2011

I need some advice from the ArcHydro community regarding my current workflow that I would like to improve in using ArcHydro to determine where structures (Bridges; Major and Minor Culverts) will be required along my railway alignment I'm using the 90m SRTM DEM tiles and ArcHydro to generate watersheds along a railway alignment where structures will be required. At current my workflow entails using the preliminary locations determined by the engineers as BatchPoints to generate Watersheds. I complete all the preprocessing steps in ArcHydro and using the Trace Flow Path tool to generate Flow Paths that run through the location of the rail alignment where drainage lines were generated from the stream grid. I looking for an more automated approach to determine where structures (Bridges; Major and Minor Culverts) would be required along the railway alignment. I thought of the following approach and would like comments and suggestion in improving my approach. New Approach: I would regenerate the Stream Grid using a finer Stream Threshold to generate more Drainage Lines. I then would generate Confluence Points from the Drainage Line. I would generate a buffer wide enough along the Railway Alignment and select the Confluence Points and export those that fall within the buffer and append them to the BatchPoint Feature Class to use them as first run to generate watersheds along the railway alignment and make adjustments to the locations based on the railway alignment and prelimary locations of the structures supplied by the engineers. Any suggestions to improve my approach will be appreciated. Regards

‎05-14-2011

Just a note HEC has posted on their site that they are working on an updated version of GeoRAS as well as HMS for ArcGIS 10 and should be available this summer. Regards

‎05-14-2011

The ArcHydro team have released an update version of ArcHydro 2.0 that can be found on their ftp site that based on my experience has resolved the problems with HydroID's and Adjoint Catchment generation. Ensure that you uninstall any previous ArcHydro versions as well as APFramework. Regards

‎05-14-2011

Hi everyone Just an update, ArcHydro 2.0.1.47 is available from the ESRI ftp server. It has resolved a lot of the errors that I was receiving with regards to problems generating HydroID's and Adjoint Catchments. I have also seen that HEC-GeoRas and HEC-HMS are currently being updated for ArcGIS 10 and should be available this summer according to HEC's website. A question that I have if anyone knows, will ArcHydro 2.0 final support ArcGIS 10 Terrain Datasets and Mosaic Datasets? Regards

‎05-14-2011

Hi Mark I resolved the errors and the empty adjoint catchment by uninstalling ArcHydro and installing the latest version from the ESRI ftp server, thanks for you advice. Regards

‎05-14-2011

I would like to find out from the user community that is involved in the development of Arc Hydro for ArcGIS 10 if ArcHydro 2.0 will support Terrain Datasets as well as Mosaic Datasets as inputs to the Terrain Preprocessing model? Regards

‎05-14-2011

Arc Hydro uses your temp folder to complete a lot of its calculations. It's always recommended to empty your temp folder on a regular basis. This might resolve your problem, by removing temporary files that Arc Hydro uses in which case it will force Arc Hydro to re-create them. Hope this helps. Regards

‎05-07-2011

Hi Mark Thanks for the suggestion, I'll let you know if I come right. Regards

‎05-05-2011

I have run all the preprocessing steps with success until I reach "Adjoint Catchment". If I run the tool from the toolbar it processes all the catchments and drainage lines based on the amount of records found in the attribute table, yet it outputs an empty feature class. If I run the "Adjoint Catchment" tool from the toolbox it process all the records and reports the following error: "No records found for HydroID assignment". I have ensured that both the drainage lines and catchments have HydroID's as well as Next Down Stream ID's. I have also ensured that my temp directory has been emptied. Any advice to solve the following would be appreciated. Unfortunately my study area is too large to upload the drainage lines and catchments. Regards

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My Ideas

Latest Contributions by PeterWilson

Zonal Statistics as Table: Overlapping Polygons: Solution Required

Arc Hydro 2.0 for ArcGIS 10: Copy an existing model

Re: Railway Structures Identified: Workflow Assistance

Railway Structures Identified: Workflow Assistance

Convert Polyline to Raster?

Conditional Statement: Generate new raster based on intersection of two rasters

Railway Alignment: ArcHydro Workflow

Re: HEC-RAS and ArcGIS 10 dilemma

Re: Catchment Polygon/Adjoint Catchment Problem

Re: ArcHydro in ArcGIS 10

Re: ArcHydro 9 & 10: Adjoint Catchment: Empty Feature Class

ArcGIS 10: ArcHydro 2.0 Features

Re: Assign Hydro ID Crashes Arcmap

Re: ArcHydro 9 & 10: Adjoint Catchment: Empty Feature Class

ArcHydro 9 & 10: Adjoint Catchment: Empty Feature Class

Editing: Autocomplete Polygon

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