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West India Consultancy Services
Surveying & Designing Solutions
+91-9898038008,+91-9737628768
Welcome to
West India Consultancy Services
Drone Survey
DGPS Services
West India Consultancy Services being highly trained professionals specialize in advanced land surveying techniques and many other relevant services for both residential and commercial clients. Utilization of innovative technologies ensures our clients receive the most accurate survey data. We follow safe work practices and excel at delivering a variety of services as elaborated below
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DGPS/Gps Survey: Static GPS, where the receiver is stationary, is the original GPS method. And it is still the preferred approach to establishing the most accurate positions, the control. And some components of static GPS control methods are useful in GPS methods where the receiver is on a moving platform. These methods include real-time kinematic, RTK, and Differential GPS, DGPS work. It is interesting that there are some elements of static GPS, such as station diagrams, observations logs and to-reach descriptions that would rarely, if ever, be necessary in high-production dynamic work. And finally, there are aspects, though handled a bit differently in both categories of work that have utility in each. In this lesson, we start to get into the real details of how GPS work is done.
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DGPS INTRODUCTION :-The advanced version or the enhancement to Global Positioning System or the GPS is DGPS i.e.Differential Global Positioning System or DGPS. DGPS was developed to meet the needs of positioning and distance measuring. It provides better and improved location accuracy than GPS. The underlying premise of differential GPS (DGPS) requires that a two DGPS receiver unit operated sequentially, one is stationary called as Base unit and other is moving called as Rover unit.
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DGPS Base and Rover Station Equipment:-The advanced version or the enhancement to Global Positioning System or the GPS is DGPS i.e.Differential Global Positioning System or DGPS. DGPS was developed to meet the needs of positioning and distance measuring. It provides better and improved location accuracy than GPS. The underlying premise of differential GPS (DGPS) requires that a two DGPS receiver unit operated sequentially, one is stationary called as Base unit and other is
moving called as Rover unit.
1. Static Surveying
Concept: Static surveying is a post-processed GNSS technique that involves setting up GNSS receivers to collect raw satellite data for an extended period. The collected data is then processed later to achieve the highest possible positional accuracy.
Key Characteristics:
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Observation Period: Receivers are left stationary over points for relatively long durations, typically from 30 minutes to several hours, or even days. The longer the observation, the better the accuracy and ability to resolve ambiguities.
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Data Collection:
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High-quality, dual-frequency GNSS receivers are used to collect both code-phase and, crucially, carrier-phase measurements from all visible satellites.
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Receivers log this raw data internally (e.g., to an SD card).
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No Real-Time Link: During the fieldwork, there is no real-time communication link required between the receivers. This makes it ideal for remote areas where communication infrastructure is poor.
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Post-Processing: This is the defining feature. After the field session, the logged data from all receivers is downloaded to a computer. Specialized GNSS post-processing software is used to:
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Baseline Processing: Compute precise 3D vectors (baselines) between the reference station(s) and the unknown points.
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Ambiguity Resolution: The software meticulously resolves the integer ambiguities of the carrier phase measurements. This is the key to achieving high accuracy.
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Error Mitigation: Sophisticated algorithms are applied to model and reduce various errors like atmospheric delays (ionospheric and tropospheric), satellite orbit errors, satellite clock errors, and receiver clock errors. By observing for long durations, errors tend to average out or can be more accurately modeled.
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Network Adjustment: If multiple baselines and control points are involved, a network adjustment can be performed to achieve the most consistent and accurate coordinates across the entire survey area.
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Benefits:
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Highest Accuracy: Achieves the absolute best possible positional accuracy, often in the millimeter to sub-centimeter range (3−10 mm horizontal, 5−20 mm vertical).
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Long Baselines: Capable of processing very long baselines (tens to hundreds, even thousands of kilometers) especially when using data from Continuously Operating Reference Stations (CORS) networks.
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Robustness: Highly robust against momentary signal outages or poor satellite geometry during observation, as errors are averaged out or can be resolved during post-processing.
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Independent Fieldwork: No need for real-time communication infrastructure in the field.
RTK Surveying
RTK relies on measuring the carrier phase of the satellite signal, which is much more precise than the code-phase measurement used by standard GPS. The system involves two main receivers:
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Base Station (Reference Receiver): This is placed on a point with known, fixed coordinates. It continuously tracks the satellites and calculates the instantaneous errors in the signals (due to atmospheric delays, satellite clock drift, etc.) by comparing the received data to its own known position.
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Rover (Mobile Receiver): This is the unit carried by the surveyor to collect points. It receives the satellite signals and the Base Station's correction data via a communication link (usually radio or cellular internet, known as Network RTK or NTRIP).
The Rover uses the Base Station's corrections to instantaneously resolve the integer ambiguity (the unknown number of whole wavelengths between the satellite and the receiver). Once solved, the Rover achieves an "RTK Fixed" solution, providing a centimeter-accurate position on the spot.
Here's an image illustrating the concept of RTK surveying, showing the Base Station, Rover, and satellite communication:
Benefits of RTK for Topographical Surveys
RTK surveying is ideally suited for creating detailed topographic maps due to its key advantages:
1. Massive Increase in Field Efficiency (Speed)
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Real-Time Data: The most significant benefit is that the surveyor gets a final, high-accuracy coordinate immediately. There is no need to occupy a point for long periods, as required by traditional static GPS, or to return to the office for intensive post-processing.
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Rapid Point Collection: Surveyors can walk or drive the site, collecting hundreds of points instantly to create dense, detailed topographical models, contour lines, and Digital Elevation Models (DEMs).
2. Centimeter-Level Accuracy
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RTK provides positional accuracy typically in the range of ±1 to 3 cm horizontally and slightly higher vertically. This level of precision is crucial for:
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Engineering and Design: Accurately defining grades, slopes, and drainage features for construction and infrastructure projects.
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Volume Calculations: Generating accurate surfaces for calculating earthwork cut and fill volumes.
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