نشریه مهندسی نقشه برداری و اطلاعات مکانی
سال پنجم شماره 1 (پیاپی 17، اسفند 1392)

Tropospheric delay is one of the main error sources on GNSS measurements. Neutral atmosphere refraction causes Tropospheric bias. One may uses GNSS observations to estimate the zenith tropospheric delay on static mode but kinematic tropospheric delay estimation is not a standard method. The kinematic estimation is in particular importance for hydrographic community whereas they have GNSS receiver onboard. The distance of these receivers to mainland stations are rather long for kinematic tropospheric estimation. The Precise Point Positioning (PPP) method is an alternative to traditional relative positioning methods. In this paper this approach is developed using Bernese 5 software and the NRCAN online PPP service (CRS-PPP). A static observation is used as a reference data for kinematic results. The results are rather promising for atmospheric applications of GNSS over oceans and open seas.

In this paper, a time series of Precipitable Water Vapor (PWV) in 2 hour intervals for year 2005 has been estimated for Tehran region using observations of National Cartographic Center (Iran) permanent GPS station. Zenith Total Delay (ZTD) which is obtained from analysis of GPS observations is subtracted from Zenith Hydrostatic Delay (ZHD) that is determined from surface pressure, temperature and humidity. By applying transformation factor on the result of subtraction of ZTD and ZHD, namely Zenith Wet Delay (ZWD), PWV was provided. The results show that the maximum and minimum PWV occur in July and February with monthly average of 23.3 and 8.2 millimeters respectively. Also maximum variation during one month occurs in August with standard deviation of 6.5 millimeters. Good coherence between our results and UNB3m model validates estimated PWV

In order to study crustal deformation and slip rates on active faults, there are different models. One of them is Block Model which includes the effects of block rotation and elastic strain accumulation consistent with a simple model of the earthquake cycle. Geodetic observations, especially Global Positioning System measurements, of inter-seismic deformation provide constraints on the partitioning of fault slip across plate boundary zones, the spatial distribution of both elastic and inelastic strain accumulation, and the nature of the fault system evolution. Block motions, fault-slip rates, elastic coupling, and internal block strain rates are determined simultaneously using a linear estimator with constraints from both geodetically determined velocity fields and geologic fault-slip rate estimates. In this research, we are focusing on Block motions in N-E Iran area which indicate Euler pole parameters determination. Clockwise block rate rotations from 0.1 to 6.7 degrees per Myr with standard deviation ±0.02 to ±1.7 degrees per Myr were obtained for different blocks considered in this study.

Landslides are natural disasters that can cause extensive damage to both property and life every year, and therefore, generating landslide susceptibility map is essential for planning future developmental activities. The objective of this paper is to analyze the relationship between landslide locations and landslide related factors by applying regression tree algorithm in a GIS environment. In this research Classification and Regression Trees (CART) is used for generating landslide susceptibility map. Eight causal factors in landslide occurrence are chosen, namely; slope, aspect, curvature, land cover, lithology, distance to river, distance to faults and distance to roads. Data of 104 sample points of observed landslides in Mazandaran Province, Iran, are applied as training data and the rest are used as test data for pruning regression tree. The results indicated that the landslide susceptibility map has the most intensity with two factor maps; lithology and slope.

Within the last few years, such terms like Volunteered Geographic Information (VGI), User Generated Geographic Content (UGGC) and Crowdsourcing appeared, and involved in the production a completely new phenomenon in public collecting spatial data and define a new source of data. The main feature of these resources is extensive users with constantly growing number who are collecting spatial data voluntarily. At the beginning, these collaborative environments, only includes the two-dimensional spatial data, but now possibility to collect three dimensional data increased and most users are able to collect 3D data. Adding three dimensional data to VGI projects is an important step, not only because of the fact that we are living in a 3D world, but also because of three dimensional data cause development in most fields. In addition, it is useful for spatial analysis in various applications. In this study, data structures and methods for producing interactive 3-dimensional city models based on UGGC, is evaluated. Because of collecting UGGC with public participation through web-based database, it is necessary to share these data with users through a standards-based Web site. Therefore, in order to transfer 3D data in web with more interoperability, some specifications and standards are developed. In this paper some of them which are more related to 3D UGGC and are important in 3D VGIs have been discussed. Although one of the main characteristics of UGGC, is fast growing and increasingly users, But precision and completeness of these data is a lateral discussion. So In this study, the accuracy and adequacy of UGGC as a substitute for professional data are also discussed.

Harmful Algal Bloom (HABs) has caused a massive fish kill and discoloration in Persian Gulf from September 2008 to February 2009. Timely detection of HABs is critical for assessment, monitoring and management of red tide impacts. Remotely sensed data provide very valuable capabilities for this task. For practical examination of these capabilities, multi temporal data of MODIS with spatial resolution of 1 KM acquired from September 2008 to February 2009 has been used. Fluoresce line Height FLH (Wm-2µm-1Sr-1) has been computed for all data sets. The FLH data have been ordinarily classified. The resulting classified data have been compared with field measurements of the red tide. Considerable agreements between the FLH classes and filed data of red tide concentrations has been observed. In contrast, to FLH data, chlorophyll data provided by the traditionally used band-ratio, lead to false information about the presence of red tide. Comparison of the time series of MODIS image for the period of six months from September 2008 to February 2009 has shown that, the intensity of blood has increased in February. Also, in September 2008, blood has started from west and has expanded to eastern parts of the Persian Gulf. Comparison of the sea surface temperature (SST) data with those of the FLH, has shown that red tide tend to bloom in relatively cooler waters (18-20 ◦c). Although, it does not mean that cooler waters are a good indicator of the presence of a red tide in Persian Gulf. The main conclusion of research is that MODIS FLH data provides very valuable information for observation and monitoring of the red tide.

With the development of satellite technologies and the development of processing algorithms, coupled with the use of SAR sensors, allowing for ground moving target detection and velocity determination has been provided by remote sensing satellites. Although previously airborne SAR systems had been used specially for military uses, nowadays this feasibility has been provided from space born SAR systems for civil applications such as traffic monitoring and search and rescue. In this study, the process of SAR image formation and the effects of moving components have been simulated in MATLAB and the results analyzed. Also the methods of detecting moving targets such as ATI and DPCA have been implemented on simulated images. Finally, these methods were implemented on real TerraSAR-X images to detect moving targets.