This paper compares the precision and accuracy of five current global positioning system (GPS) receivers—Trimble ProXR, Trimble GeoXT without WAAS, Trimble GeoXT with WAAS, Trimble GeoExplorer II, and an HP/Pharos receiver. Each of these receivers, along with other similar units, are frequently used today for data collection and integration within a geographic information system (GIS). To compa...

Navigation using GPS generally requires that the user track four satellites to resolve his 3-D spatial position and time bias. There are several reasons why it is desirable to navigate while tracking only three satellites: -The proposed 18 satellite GPS constellation will exhibit substantial periods of poor four satellite geometry over large geographic areas several times a day. -Failure of a G...

The vulnerability of civil GPS receiver to interference may be intentional or unintentional. Among all types of interference, replay attack intended as the most dangerous intentional one. The signal structure of replay attack is almost the same with the satellite signal. The interference effects can be reduce with the design of an appropriate filter in the receiver. This paper presents two meth...

The Global Positioning System (GPS) signals are very weak signal over wireless channels, so they are vulnerable to in-band interferences. Therefore, even a low-power interference can easily spoof GPS receivers. Among the variety of GPS signal interference, spoofing is considered as the most dangerous intentional interference. The spoofing effects can mitigate with an appropriate strategy in the...

This study evaluated the positioning accuracy of moving forest harvesters using global navigation satellite system (GNSS) signals under a canopy, and developed approaches for forecasting mature spruce canopy cover. Real-time kinematic with Trimble R12 receiver on top harvester achieved high accuracy, 86% observations meeting maximum precision 8 mm. However, presence cover hampered GNSS’s perfor...

The present paper analyzes the influence of the forest canopy on the accuracy of the measurements performed by global positioning systems (GPS) receivers. The accuracy of a large set of observations is analyzed in the present research. These observations were takenwith a GPS receiver at intervals of one second during a total time of an hour in twelve different points placed in forest areas char...

Aboveground biomass, volume, and basal area are among the most important structural attributes in forestry. Direct measurements cost-intensive time-consuming, especially for old-growth forests exhibiting a complex structure over rugged topography. We defined methodology to optimize plot size (total) sampling area, allowing with tolerable error be estimated. The was assessed by analyzing semivar...