Improving Height Accuracy of the Hanheld GPS Receiver

Abstract

Elevation of ground points is one of the parameters necessary in various surveying and engineering projects. One of the techniques of determining point elevation is the Global Positioning System (GPS). Accuracy of the obtained coordinates using GPS depends on particular reasons such as the type of GPS receiver used and observation technique adopted. Recently, handheld GPS receivers were manufactured mainly for the sake of navigation. These receivers are cheaper than geodetic GPS ones. However, the accuracy of point coordinates they produce needs to be checked. Previous studies concluded that accuracy of elevations obtained using handheld receivers is worse than that of planimetry. In this research work, investigation of improving elevation accuracy obtained using handheld GPS has been carried out using regression analysis. Results show that using simple linear regression and four points as control, height accuracy can be improved from 7.68m RMSE to 3.45m RMSE (55% improvement) and when using three control points accuracy is improved from 7.68m RMSE to 4.38m RMSE with 43% improvement.

Introduction

The introduction of the Global Positioning System (GPS) has significantly advanced geoinformation sciences by providing accurate, reliable, and time-efficient positioning data for surveying and mapping. Since the first handheld GPS receiver (Magellan NAV 1000) was introduced in 1988, handheld GPS technology has become smaller, lighter, more affordable, and more capable. Modern handheld receivers can track multiple satellite constellations (GPS, GLONASS, Galileo, BeiDou, and QZSS), and dual-frequency receivers further improve positioning accuracy by reducing ionospheric errors. Despite these advancements, handheld GPS units generally provide lower accuracy than geodetic receivers, particularly in vertical (height) measurements.

Handheld GPS receivers are widely used because of their portability, low cost, and suitability for navigation, GIS data collection, and small-scale mapping. In contrast, geodetic GPS receivers offer centimeter-level accuracy but are significantly more expensive and are mainly used for high-precision surveying. Previous studies have shown that handheld GPS can achieve horizontal accuracies ranging from approximately 2 to 4 meters under favorable conditions, making them suitable for mapping at moderate scales. However, vertical accuracy is consistently poorer than horizontal accuracy due to satellite geometry, multipath effects, and atmospheric influences.

Several researchers have investigated methods to improve handheld GPS performance. Studies have demonstrated that processing raw GPS observations, selecting measurements with favorable satellite geometry, and applying least-squares adjustment techniques can significantly reduce horizontal and vertical positioning errors. Modern handheld receivers capable of recording raw GNSS observations also support differential GNSS and Precise Point Positioning (PPP), further enhancing accuracy under suitable conditions. Nevertheless, height measurements remain less reliable than planimetric coordinates.

This study builds on the work of Mohammed Fator and Zomrawi (2015), who evaluated the accuracy of the Garmin eTrex handheld GPS using 25 control points in Khartoum, Sudan. Their results showed a horizontal accuracy of ±3.16 m and a vertical accuracy of ±7.68 m when compared with Differential GPS (DGPS) observations. Using these data, the present study aims to develop a regression-based method to improve the vertical accuracy of handheld GPS-derived elevations while maintaining the practical advantages of low-cost handheld receivers.

Conclusion

The height accuracy of points obtained using handheld GPS is not suitable for topographic mapping of contour interval less than 15m. So, it is not recommendable to use handheld GPS in any precise topographic survey, rather it can be used in preliminary surveys. However, if regression approach is applied using 3 control points the height accuracy of less than 5m can be obtained. This will allow production of 10m contour interval maps. Using modern professional handheld units that can track multiple signals and applying correction using differential or PPP methods can allow accuracy of cm to decimeter level. Hence can be used to produce 1 meter contour interval topographic maps.

References

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Copyright

Copyright © 2026 Ismat M. Elhassan, Hasan Bilani. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.