GPS World, March 2015

ON THE EDGE The Precision to Carry On Nicholas DiGruttolo W hen asked to do a small survey job overseas we were concerned about shipping bulky and expensive survey equipment Shipping costs are not trivial Add to that the real possibility that your survey equipment may be confiscated by the local authorities as ours was in Djibouti and the cost of shipping equipment becomes a substantial part of the overall job There should be alternatives especially if accuracy requirements are not stringent Faced with this problem for a second time we considered a new receiver system that has many advantages over conventional survey grade GNSS receivers It is small lightweight and low cost without sacrificing performance making it ideal for precision surveying in remote areas of the world and for traveling to the job site by commercial airline All the components including the tripods rods and batteries are constructed from commercial off the shelf COTS components A complete base and rover kit fits in a baseball bag and weighs less than 10 kilograms The kit is sized and approved as carry on luggage The system is scalable from a simple single frequency semi mobile receiver for control networks and some semikinematic mapping applications to a dual frequency network RTK solution The system comes with free processing software that supports carrier phase relative positioning in real time and post mission as well as precise point positioning PPP and CA code differential correction The software is designed with a simple user interface for easy selection of base and rover data or automatic data download of the closest Continuously Operating Reference Station CORS from the U S National Geodetic Survey database The system fills a gap between survey applications where centimeterlevel precision is an absolute necessity and mapping applications where meter level is tolerable The product offers sub foot precision in most cases and centimeter precision in ideal situations Our team recently performed topographic mapping of an oil refinery site in Saudi Arabia and surveyed a precise elevation network in Sarasota Fla to research the effects of sealevel rise The small size of the COTS components simplified transport to Saudi Arabia eliminating additional airline baggage fees and easing import through customs Researchers performing the sea level study reduced field time by increasing the number of receivers needed to observe a robust vertical control network Oil Refinery The oil refinery project entailed mounting a GNSS antenna on the roof of an off road vehicle and driving multiple transects around the 18 kilometer perimeter of the site to record the elevation of the terrain Kinematic data was recorded at 1 Hz using a GPS only version of the COMPONENTS easily pack into a baseballstyle case COMPLETE SURVEY SET including GNSS receiver antenna battery and cables fits in a small handheld plastic case FIGURE 2 Sea level rise monitoring network showing increased tie points and redundancy as a result of adding the extra lightweight precision receivers to the survey grade receivers COPYRIGHT 2015 NORTH COAST MEDIA LLC All rights reserved No part of this publication may be reproduced or transmitted in any form by any means electronic or mechanical including by photocopy recording or information storage and retrieval without permission in writing from the publisher Authorization to photocopy items for internal or personal use or the internal or personal use of specific clients is granted by North Coast Media LLC for libraries and other users registered with the Copyright Clearance Center 222 Rosewood Dr Danvers MA 01923 phone 978 750 8400 fax 978 750 4470 Call for copying beyond that permitted by Sections 107 or 108 of the U S Copyright Law PRIVACY NOTICE North Coast Media LLC provides certain customer contact data such as customers names addresses phone numbers and email addresses to third parties who wish to promote relevant products services and other 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