The Effect of Broadleaf Canopies on Survey-grade Horizontal GPS/GLONASS Measurements

A study was conducted to empirically determine the degradation of survey-grade GPS horizontal position measurements due to the effects of broadleaf forest canopies. The measurements were taken using GPS/GLONASS-capable receivers measuring C/A and P-codes, and carrier phase. Fourteen survey markers were chosen in central Connecticut to serve as reference markers for the study. These markers had varying degrees of sky obstruction due to overhanging tree canopies. Sky obstruction was measured by photographing the sky with a 35mm reflex camera fitted with a hemispherical lens. The negative was scanned and the image mapped using an equal- area projection to remove the distortion caused by the lens. The resulting digital image was thresholded to produce a black-and-white image in which a count of the black pixels is a measure of sky-area obstruction. The locations of the markers were determined independently before the study. During the study, each marker was occupied for four 20-minute sessions over the period of one week in mid-July, 1999. The location of the study markers produced relatively long baselines, as compared with similar studies. We compared the accuracy of GPS-only vs. GPS&GLONASS as a function of sky obstruction. Based on our results, GLONASS observations did not improve or degrade the accuracy of the position measurements. There is a loss of 2mm of accuracy per percent of sky obstruction for both GPS only and GPS&GLONASS.

Surplus Labor in Indian Manufacturing: Evidence from the Annual Survey of Industries

In this paper we analyze state level data for total manufacturing constructed from the Annual Survey of Industries for the period 1986-2000 using the nonparametric method of Data Envelopment Analysis (DEA). We assess the extent of surplus labor in the manufacturing sector in the individual states in India. The study also investigates whether the same states show the maximum incidence of surplus labor every year in the sample period and if there any evidence that the extent of surplus labor in manufacturing has been reduced or eliminated in the post-reform era. Our study shows the presence of considerable measure of surplus labor in all of the years in a majority of the states. Things have worsened rather than improved after the reform. Also, the regional distribution of surplus labor has remain fairly unchanged with the same states performing inefficiently both before and after the reform.