Salis vol. 64, no. 1

March 2004

 

Accretion, Avulsion, and Riparian Boundaries

Andrew C. Kellie

 

This paper discusses the role of accretion and avulsion in fixing the riparian boundary.  Accretion, a slow and imperceptible change in the location of a stream, changes boundary location as the stream moves. Avulsion, a rapid and perceptible change, affects no change in the boundary. In addition to general rules regarding riparian boundaries, this paper considers the hydrologic aspects of stream movement and discusses specific boundary cases involving boundary change by accretion and avulsion.

 

A Better Way to Turn an Angle

Thomas S. McGrath

 

In classical geodesy we have the FGCC Standards and Specifications to help control the quality of our work. Upon examination, however, those of us in the Surveying Professions realize that these standards and specifications do not always fit well with certain types of surveys when measuring short distances. Shorter distances are a particular necessity in non-geodetic work. Classical traversing, triangulation, and trilateration have been replaced with Global Satellite Surveying techniques in most instances. GPS is being used for primary control, photogrammetric control, and even for cadastral control over relatively small areas typical of land subdivision work. This raises the practical question of how surveyors and geometricians should proceed in the making of short measurements, i.e., those measurements less than 200 meters (about 700 ft). This distance is the practical limit for optical resolution of one second of arc. They constitute more than 95 percent of all observations made in the more traditional surveying. This article examines a new and better way to observe angles, given the shorter lengths more common to engineering and land surveying.

 

The Expert Witness: The Impact of Kuhmo 

Salvatore A. Marsico

 

The expert witness is a valuable person and, at times, indispensable for the purposes of resolving the legal case. In the federal courts of the United States, testimonial evidence is permitted to be presented to the jury or the judge under strict rules. These rules are referred to as the Federal Rules of Evidence. During the past twenty years, many product liability cases have been decided by the United States Supreme Court. These decisions have altered how the expert witness is utilized by the litigating parties in all other types of cases. In recent times, no other cases have impacted the Federal Rules of Evidence (and testimony offered by expert witnesses) more than the cases of Dow Pharmaceuticals and Kuhmo Tires. It is the intent of this article to discuss the nature of these cases and their impact on the expert witness and the Federal Rules of Evidence. Background to these rules, including admissibility and weight of evidence, and sufficiency of expert testimony, is also provided.

 

Stones and “Bones” Set by William (Billy) Octavius Owen: A Brief Historical Account of Living and Surveying in Wyoming

J.D. “Sam” Drucker

 

In November 2000, while helping to create the Bureau of Land Management’s (BLM) Geographic Information System (GIS) base layer—the Geographic Coordinate Data Base (GCDB)—I stumbled upon a Government Land Office (GLO) survey plat that has enlightened my views of surveying and Wyoming history. This plat (Figure 1) was drawn from work conducted by William (Billy) O. Owen during March and April of 1881 in Township 24 North, Range 77 West (T24NR77W).

Noted in the center of the plat is a line of section corner monuments labeled as “Mastodon Bones.” The idea of relocating and collecting some of these “bone” section corners was intriguing, and I found myself researching the methods needed to accomplish this task. While discussing with John Lee (cadastral chief, Wyoming State Office [WYSO] BLM) my intent to locate and recover the “bone corners,” I realized that others within the Bureau were equally eager to recover them.

 

Statistics and Adjustments Explained

Part 3: Error Propagation

Charles D. Ghilani

 

Error propagation is an important concept in least squares adjustments. Random instrumental errors (such as miscentering, reading, and pointing) propagate into our observed angles, distances, and elevation differences. This paper looks at how error propagation can be used in developing a sound stochastic model for weighting observations in a least squares adjustment. The paper will also explore the uses of error propagation in post-adjustment statistics, such as error ellipses.

 

Investigation into Small-format Digital Camera Sensors for Development of USDA GIS of Crop Compliance

Stacey D. Lyle, RPLS

 

The use of small-format DF and DFV digital camera imagery in GIS-based crop compliance monitoring was investigated. Digital frame offers higher spatial resolution with larger image size but requires longer image write times. Digital frame video, on the other hand, offers faster write speed but, typically, has smaller image size. Evaluation and comparison of the two types of sensors support recommendations for discontinuing the use of 35-mm slide film.

 

Integrating Pseudo-Hydrologic Logic in Road Extraction

Yafit Cohen, Maxim Shoshany, and Yerach Doytsher

 

A pseudo-hydrologic method was developed for road extraction from medium-resolution satellite images. Transformation of image brightness into a Pseudo Digital Elevation Model (PDEM) allows emulation of hydrologic flow. Flow direction and flow accumulation are then calculated for each image pixel using hydrological GIS routines. Road segments are recognized by setting a minimal threshold to the pseudo-flow accumulation. Implementation of the technique to extract major roads and railways from a Spot-panchromatic image yielded high recognition accuracy (90 percent). In another experiment, this technique was used to extract roads in dense urban areas from multispectral IKONOS images. Moderate success (70 percent) was achieved in this task.

KEYWORDS: Road extraction, hydrologic modeling, low-level algorithm

 

Local Geoid Determination Using Global Positioning Systems

Kandiah Jeyapalan

 

It is well established that elevations determined by global position systems are above reference ellipsoid heights and should be corrected for geoid undulation to determine the orthometric height or mean sea-level elevation. The paper describes research performed at Iowa State University in cooperation with Iowa Department of Transportation to determine the local geoid, Nl, with ±2 cm accuracy for a countywide area, study its variation with time, and develop a method to predict the future local geoid with ±2 cm accuracy. This paper describes the data collection method, provides the results of three observations at six-month intervals for studying the variation of Nl with time; explains a method developed for predicting Nl and determining agreement with a fourth observation; and describes a procedure for establishing elevation control by global positioning systems for leveling and for establishing control in a real-time kinematic global positioning systems project.