Various techniques and equipment for shallow coring are available see Chapters The hand or soil auger is the most basic of the mechanical drills. Sophisticated techniques are generally driven by engines and hydraulic components see Figure 1. Numerous and various systems hammer, weights, etc. In periglacial geomorphology, for instance, coring and borehole instrumentation is very common since thermal subsurface conditions are important sources of information e.
In landslide research, coring is an in situ testing method to measure geotechnical properties with the cone penetration test CPT. In sediment budget studies coring allows, in combin- ation with dating results of organic samples, estimates of sedimentation rates.
Sampling of soils, sediment, or debris is frequently combined with coring core sampling and is also applied directly at the surface, to outcrops, or in excavated pits trenches and tun- nels see also Chapter Apart from clastic sediment, sampling of water and ice is also common in many geo- morphological studies.
The number of necessary samples and the design of sample selection can vary considerably from task to task. Bias and measurement errors in sampling are crucial issues and should be minimized through careful sampling strategies and treat- ments. In general, drawing conclusions from only a few samples should be avoided. A short overview regarding sampling strategy and further literature is given by Rice and a good practice guide for sampling in glacial and periglacial environments is given by Hubbard and Glasser Figure 1 Sediment coring in a high alpine bog.
A specially constructed mounting rack has been developed to facilitate the removal of the vibro-corer and the sediment cores. An Overview Author's personal copy Within the past few years GPS receivers have been widely distributed, ranging from car navi- gation systems to portable mobile phones.
Due to the technical prin- ciples of GPS, the local position can be accurately determined from several meters to a few millimeters. Although low-accuracy positioning is performed by low-cost commercial handheld GPS devices e. Global positions are determined by triangulation using radio signals from 24 orbiting satellites.
GPS receivers generate an identical code, which is correlated to the trans- mitted satellite code. The time delay between the two signals is used to calculate the distance between the two devices. This delay between the codes represents the travel time of the radio waves, which allows for the calculation of the distance range. In general, two techni- ques of high-accuracy GPS measurement can be distinguished: Both techniques require two dual-frequency receivers for signal correction, allowing for a differential positioning referred to as differ- ential GPS.
What distinguishes them is the timing of the signal correction, which is either performed in real time dur- ing the survey or after the survey as postprocessing. Static survey involves postprocessing correction of two receiver signals. One receiver needs to be located at a known position base station , whereas the other must be positioned on the location measured rover station. Both receivers record at the same rate over a longer period of time usually minutes to hours. Later the signal is corrected by comparing the two recorded data sets.
From the distance between the two receivers i. Static survey mode is applied for the exact positioning of single objects or repeated monitoring, for example, in land- slide monitoring Squarzoni et al. In kinematic survey mode, correction of the signal is delivered in real time real-time kinematic. Thus, the rover can move independently and it receives both the satellite signal and the correction signal from a reference station or base station.
Several methods exist to transmit the correction signal, ranging from short-distance radio transmission of nearby base stations to long-distance signals of permanent recording stations. The latter is commonly provided as a commercial service and inherently comes with extra cost.
The accuracy of this signal correction generally declines with increasing distance to the reference station baseline. Applications of real-time kinematic GPS survey include, for example, landform mapping Higgitt and Warburton, or measurement of surface movement from creeping mountain permafrost Lambiel and Delaloye, Even though GPS technology should grant the user their global position, some surface conditions can reduce the availability of satellites and data accuracy.
GPS accuracy in areas close to steep rock faces, for example in high relief areas, and under dense vegetation, satellite signals are commonly lost or jammed when the elevation angle to the satellite be- comes too small. In remote terrain, commercial corrections signals are generally not available.
They enable one to answer not only established geomorphological research questions with a higher level of precision, but also formerly unsolved geomorphological problems can be addressed today using LiDAR technology, as Fundamental Classic and Modern Field Techniques in Geomorphology: For example, LiDAR data enable semiautomated geo- morphological mapping van Asselen and Seijmonsbergen, and the determination of size, shape, or roughness of different land surfaces with a high level of detail e.
LiDAR data are commonly also used as accurate base data for different modeling approaches e. Further- more, repeated laser scan surveying provides a tool for multiple process monitoring strategies of large areas. LiDAR data in hydrological research are used to analyze erosion and deposition of river systems Lane et al. However, the cap- ability of the LiDAR system strongly depends, among other factors, on the wavelength of the laser type applied.