To enhance the Municipality's water management system and operations and address challenges with the existing water supply

 Introduction

The main objective of the Catalyste+ assignment is to focus on the water management system, however additional tasks include capacity building with respect to other departments within the municipality including cadastral, environment and information technology where possible.

Currently Copan Ruinas obtains its potable water from existing creeks flowing through the community. It collects surface water at intakes along the creek and pipes it to a treatment facility. The current facility is not operating as designed and limited treatment with chlorination is provided before it is pumped to two storage locations. One storage tank serves the lower town and the other serves the middle town. The upper town is currently served by local suppliers to the community. 

A project was undertaken in 2006 entitled "Design, Rehabilitation and Expansion of the Drinking Water and Sanitary Sewage Systems.  Feasibility study and design for the expansion of the drinking water and sanitary sewage systems of the City of Copan Ruinas and implementation of a local management model."

The above project is named as Project 1. It was a project to upgrade the existing system with an additional intake at Quebracho. This upgrade is included in the project designed in November 2006 by HYTSA (Argentinian consulting company) in conjunction with Conash S. de R.L. C.V. 

Project 1 was finance by World Vision which provided the town with the pipes, cement and reinforcing bars for the concrete. Labour was provided by the town for the project.

Copan Ruinas engineering department has proposed Project 2 which is a new intake and pipe that would supply the upper town with potable water. The plan is for it to supply a third new storage tank entirely by gravity. The first water line requires pumping to the lower and middle storage tanks.


The above exhibit is probably an aerial photo mosaic of Copan Ruinas used by the consultants in 2006 for Project 1. It could be an orthophoto but it could not be confirmed.

Initial Observations

Coordinate System

It appears that the original design used UTM 16N NAD 27 as its projection. However our initial overlay with existing Google Satellite and Open Street Map (OSM) shows that there is an offset with the geo-registration between the systems. Additional work needs to be undertaken to establish the reason for the difference.

Note: It is important to obtain the coordinates for the reference benchmarks used in drawing PG-03. See Reference Drawings.

Geographic Information System (GIS)

Governments have recognized the importance of a common base system for land management. A common coordinate system is needed to overlay land components. This includes land titles (cadastre), engineering plans, land use and environmental data. 

QGIS is an Open Source (OS) application that compares with ArcGIS which is an expensive commercial off the shelf (COTS) software. QGIS is a very powerful GIS application which is powerful, flexible and continuous to improve by the OS community.  

QGIS can connect directly with Google Earth, OSM and Autodesk's dwg drawing files. Users should be knowledgeable about coordinate systems and projections. QGIS can form the foundation for spatial data sharing within a municipality by allowing staff to overlay the cadastral fabric with other vector and raster data from different departments.

Cadastre Department

The Cadastre Department has a digital cadastre on CAD using UTM 16N NAD 27 coordinate system. Some concerns raised by the department head is that the system is back logged because previous administrations did not maintain or update the changes in parcels, and others allowed outsiders to make subdivisions without sharing the information with the municipality. 

Operationally their staff is updating parcel subdivisions as they can in the field using a Garmin 755t GPS receiver. It should be noted that the Garmin receiver is only a single phase receiver and is not a dual frequency survey grade one. Accuracies is between 2 to 3 m plus or minus. Accuracy can be increased by the average location option, saving the reading when 100% confidence status is reached (around 7 to 10 minutes). This should be repeated 4 to 8 times taken at least 90 minutes apart (to allow GPS satellite constellation to change). 

Comparing the coordinates of the municipal cadastre with Google Earth and Open Street Maps there are some alignment issues of around 6 m plus or minus. Additional checks will be undertaken.



Project 1 - 2006 Design

The following exhibit shows the limits of Project 1. There appears to be a coordinate conversion needed to correct the location of the water lines.




Project 2 - 2022 Design

The following exhibit shows the layout of Project 2. The intake to the storage tank is entirely gravity fed. There are some outstanding issues with the design coordinates. The west branch used WGS84 coordinates and the main east branch used NAD27. The exhibit shows the lines with NAD27 and WGS84. It has to be corrected.


Civil Site Plan Considerations

There are different approaches that can be applied to laying out a project site plan for construction. An civil engineering project layout for a water line normally involves the establishment of a grid coordinate system X,Y and Z for elevation. This can be achieved with a total station using an established baseline between to benchmarks or control points, or the use of GPS coordinates.

Total Station

The total station combines the functions of a transit and level. It requires a baseline and a fixed benchmark to start. It can be considered an accurate tool to layout a profile for a pipe and site areas for structures like tanks and buildings. If a fixed benchmark is not established then it may be difficult to re-establish the starting or ending point of the project.

GPS Receivers

Many engineers and technologists use GPS coordinates for their projects. Unfortunately there is a lot of confusion about how it works. Hand held GPS receivers are normally single-frequency or single-phase units typically operating on the L1 bank (1575.42 MHz). Survey grade GPS receivers are dual-frequency using the L1 and L2 for higher accuracy.

Some single frequency units provide accuracy within 1-5 meters, which can be improved to centimeter-level with DGPS or PPP techniques, although this requires longer initialization times. 

For cadastral and engineering data collection waypoint averaging is a way to increase the point coordinate accuracy.

Coordinate Reference System

There are different coordinate reference systems (CRS) which affect the data a GPS receiver presents. The most common is the World Geodetic System 1984 (WGS84) which is also referred to as earth centered earth fixed (ECEF) ellipsoid. This is the basic CRS in the GPS receivers.

The European Petroleum Survey Group (EPSG) created a standardized public registry of geodetic parameters, including coordinate reference systems (CRS), datums, projections, and units identified by a unique 4-5 digit codes such as EPSG:4326 for WGS84. These codes ensure accurate spatial alignment in GIS and web mapping. The registry is now maintained by the IOGP Geomatics Committee.

The North American Datum of 1927 (NAD27) is a horizontal geodetic datum covering North America, based on the Clarke 1866 ellipsoid. It was widely used for historical USGS topographic maps, although it has largely been replaced by NAD83.

Unlike modern geocentric systems like WGS84 or NAD83 which are centered at the Earth's center of mass, NAD27 is based on a specific survey point. This means coordinates for the same location can differ significantly (often by 100 meters or more) between NAD27 and NAD83 or WGS84.

Imagery from Google Earth and other web mapping servers uses special web projections such as WGS84 Pseudo-Mercator (EPSG:3857).

This means you need to understand the CRS of each set of data you are using because mixing data with differing CRS in a drawing or GIS application would cause errors and problems with the project.


Reference Drawings

PG-03 - Shows local benchmarks and elevations (need benchmark coordinates)
PC-03 - Shows pipeline, treatment plant and storage tank for Project 1. Coordinates not registered.



Comments

New comments are not allowed.

Popular posts from this blog

Using Google Satellite & Open Street Maps as the Base for Copan Ruinas GIS System

Image
 Using Google Satellite & Open Street Maps as the Base for Copan Ruinas GIS System Background We are all familiar with using Google Map for location and navigation with our mobile phones. We can see our track as we drive along the roads on the map. It generally falls within the width of the road, especially if we are zoomed out. Similarly we can see where we are on the map if we are looking for a restaurant or store in town. The single band GPS/GNSS (L1) receiver in our phone gives us a location within 5 to 10 m in urban areas, normally that is enough for what we need. In addition the Google satellite image also is accurate within 2 to 15 m depending on where you are in the world. We can see that when we are using it while we are walking along a street. Sometimes if we look at the image it shows that we are on the right side of the road even though we are walking along the left. This is because of the accuracies of the GNSS receiver and the google map image registration. If we ...
Read more

GPS Surveying & Drone Mapping for Public Works and Cadaster Departments

Image
  Background Historically local governments in many countries used optical survey instruments to map their cadastre and public works projects. Many municipalities establish a baseline using a survey control benchmark in the square near their municipal offices to establish a baseline to measure their surveys from.  In the Philippines the U.S. Army Corps of Engineers originally established the geographic coordinates of these control monuments using celestial observations. These coordinates have been updated with the launching of the GPS satellites by the U.S. Department of Defence in 1978.  Since then Europe, China, Russia and others have added their own constellations of satellites to augment positional accuracy and to decrease the reliance on one nation for that service. They are referred to the Global Navigation Satellite System (GNSS) as a whole for precise geo-spatial positioning, navigation and timing (PNT) services. They are named respectively Galileo, BeiDou, Glonas...
Read more

Solid Waste Stockpile Monitoring with Drone Photogrammetry on a Budget

Image
Solid Waste Stockpile Monitoring with Drone Photogrammetry on a Budget Background Solid waste stockpile monitoring involves the systematic, real-time, or periodic evaluation of waste piles to manage volume, ensure environmental safety, and maintain regulatory compliance. Modern monitoring techniques, such as 3D LiDAR scanners and UAV (drone) photogrammetry, have largely replaced manual, less accurate estimations, allowing for safe, continuous, and high-resolution tracking of waste quantities.  The following is a step-by-step example to show how local government with limited resources and equipment can monitor and manage their solid waste sites using low cost consumer drones like the DJI mini 4 Pro and single phase GPS/GNSS hand held receivers for ground control with Open Source applications like WebODM. Naturally better results can be achieved with higher grade equipment but I will show in this web blog that anyone can start even with limited resources.  The Basic Tools and Eq...
Read more