Subject: Homework #3 From: Armand Rodrigues Date: Mon, 18 Apr 2011 13:14:24 -0700 (PDT) To: hpplag@unr.edu Return-Path: X-Original-To: hpplag@twilight.unr.edu Delivered-To: hpplag@twilight.unr.edu Received: from smtp.unr.edu (gw2.unr.edu [134.197.1.109]) by twilight.unr.edu (Postfix) with ESMTP id 302F4370B for ; Mon, 18 Apr 2011 13:20:42 -0700 (PDT) Received: from localhost (localhost [127.0.0.1]) by smtp.unr.edu (Postfix) with ESMTP id 203BA1841 for ; Mon, 18 Apr 2011 13:20:42 -0700 (PDT) X-Virus-Scanned: by amavisd-new using ClamAV at smtp.unr.edu Received: from smtp.unr.edu ([127.0.0.1]) by localhost (gw2.unr.edu [127.0.0.1]) (amavisd-new, port 10024) with LMTP id 3Eae3EiI0Sy1 for ; Mon, 18 Apr 2011 13:20:38 -0700 (PDT) Received: from nm6.bullet.mail.sp2.yahoo.com (nm6.bullet.mail.sp2.yahoo.com [98.139.91.76]) by smtp.unr.edu (Postfix) with SMTP id 37FAB1FAB for ; Mon, 18 Apr 2011 13:20:38 -0700 (PDT) Received: from [98.139.91.62] by nm6.bullet.mail.sp2.yahoo.com with NNFMP; 18 Apr 2011 20:14:25 -0000 Received: from [98.139.91.2] by tm2.bullet.mail.sp2.yahoo.com with NNFMP; 18 Apr 2011 20:14:25 -0000 Received: from [127.0.0.1] by omp1002.mail.sp2.yahoo.com with NNFMP; 18 Apr 2011 20:14:25 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 263240.91069.bm@omp1002.mail.sp2.yahoo.com Received: (qmail 58582 invoked by uid 60001); 18 Apr 2011 20:14:24 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s1024; t=1303157664; bh=ElacAkf9oioFzp5DV5KnZ5I9BnGaA6C3T4rZjGpPSgE=; h=Message-ID:X-YMail-OSG:Received:X-Mailer:Date:From:Subject:To:MIME-Version:Content-Type; b=YPdde93bggx1Y2ovuJR35etxu6yIaIZZNf617F7xv5KE282OpqdPZLmCgq7BUtdHHgTf8RldtkXq7AJ1UUK1E0dfsIVIKbuWBkLhaeAgcOBLvV2moaMZDJoIulwEOB1uh6uj6Tz51phKmvF/e31uprAQS0XGADW/hBTfKrmfOts= DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:X-YMail-OSG:Received:X-Mailer:Date:From:Subject:To:MIME-Version:Content-Type; b=Z5c58CF8v/GPNvfNscfzQBIRNbZHiujnQ3HtRHyuK0c974aTwPNBclI/gCWI7sO4nKYblCH6zX2dXJ40WgxTuHtni+LuBTfuPVaNa7Ws0Qrpz/hCpdD96eqjKEevehyZiUL0yfguJISrgzfGO5xSUynXZ9timyKE4wZgLD1yVLM=; Message-ID: <828650.57440.qm@web113820.mail.gq1.yahoo.com> X-YMail-OSG: bDAzsFEVM1nluyK.zIWoDmJV4GBdqwDjEteLXXNZxthvKMG QtUqBHAnKEgUZFmiP.VKu5rk3lYzorSrfXs5FPbtwnX5vR3ofXOl_pg8Vyl7 fQ.HBF9s5MVNs_nQEUJF_3NrgThBwAMZj3lI4Q7LTb94gq8kkeEkghNmD2ar EwxZIMruHbi0AFLPOrhMF_Es4ODsfGodFdDJzE3hwdAmoarh3ECYg.wdiwu7 UsIFQmGOTHvfAhLE2FFKxytcsSIxzHArbGJ4WeMpdwzd.62MWSDX3RjLHZW6 ZKk3tDu6liPhn9uQdR1vK9tvnF5fPAQ3OL0XWupIHyKlFzrUpxY_KvnWkL_5 CxF5WINNDeEEQs6gkpjq9X377AaqNr2OrIAhGjUckgKV3qRh9BihzM4c- Received: from [75.141.252.8] by web113820.mail.gq1.yahoo.com via HTTP; Mon, 18 Apr 2011 13:14:24 PDT X-Mailer: YahooMailClassic/12.0.2 YahooMailWebService/0.8.109.295617 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-847693624-1303157664=:57440" Hey proffesor, This is Armand Rodrigues.   Problem 1: Describe the main characteristics of point-geodetic observations versus imaging techniques in terms of spatial and temporal resolution and coverage? There are two imaging techniques used to measure the earths surface and surface displacement; These are Space Geodetic Tracking Techniques and air/space born remote sensing techniques. Space geodetic tracking methods provide high temporal resolution and high accuracy. The remote sensing techniques have a lower temporal resolution but provide information with higher spatial resolution with much better coverage.   Problem 2: What is the "station motion model" and how does it enter into the analysis of point-geodetic techniques? The station motion model consist of a station fixed to the earth’s surface which have the ability to track the motion of satellites and “fixedâ€ﾝ astronomical objects such as quasars. These stations and their measurements allow for the tracking of horizontal and vertical motion of earths crust within the ITRF.   Problem 3: Which space-geodetic techniques provide the origin of the reference frame with respect to the center of mass and which provide the scale? Why? VLBI, SLR, LLR, DORIS, GNSS, and PRARE provide the origin of the reference frame with respect to the center of mass. The scale or geokinematics is provided by altimetry, InSAR, GNSS, VLBI, SLR, DORIS, and tide gauges.   Problem 4: Explain the principle of GNSS reflectometry. The Accronym GNSS refers to the Global Navigation Satellite System. The most well known of these, at least in the U.S., is the GPS system. GNSS uses multiple satellites and fixed earth stations to triangulates positions of these fixed points. GNSS can be used to determine movements of the earth. 　 Problem 5: Why are laser retroreflectors on satellites like Global Navigation Satellites, altimeter satellites, and other satellites that use geometrical principles important? Laser Retroreflectors allow for satellites to be accurately tracked and accurate orbital paths to be determined. Since these have a very high resolution and accuracy SLR can use small perturbations in a satellites orbit to determine changes in the gravity field.   Problem 6: Explain briefly the principle of InSAR and identify the major limitations for accuracy and and applicability. How could these challenges be addressed? To use InSAR radar signals are radiated from a moving platform and are reflected back to the antennae from the surface of the earth, then the intensity of the phase and reflected signal are measured. Remaining issues with InSAR include combination of imaging and point measurement, connection to a global geocentric reference frame, and reduction of atmospheric effects. All of these can be improved upon by advancment of the transforms used to calculate the data received.   Problem 7: What are the main characteristic of in situ, airborne and spaceborne gravity measurements in terms of temporal and spatial resolution, as well as accuracy as function of spatial and temporal scale? Initially gravity was measured in situ by determining in situ leveling and combining it with tracking of airborne or space borne instrumentation. Problems encountered include difficulty of measuring gravity and topographic height on a world wide scale, high error associated with long wave length, and a theory which has not advanced beyond its first order. The advantage of in situ and airborne gravity measurements is high spatial resolution of short wave lengths. Since then geodist have used measurement of satellite perturbations to determine changes in gravity along the satellites determined orbit. This method has a high spatial and temporal resolution as long as the orbits of the satellite are accurately known.   Problem 8: Explain the principle of GRACE and its main limitations in terms of accuracy. GRACE maps the Earths gravity field by making accurate measurements of the distance between the 2 satellites using GPS and and microwave ranging. Limitations in accuracy of GRACE include sensor accuracy, disturbances, spatial-temporal sampling, and calculations ( parameterization, modeling, representation).