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Topic: Chart datum

Related Topics

geodetic datum

geodectic datum

geographic datum

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	Chart datum - Wikipedia, the free encyclopedia
		The chart datum is the level of water that charted depths displayed on nautical charts are measured from.
		Chart datum is height of water at the lowest spring tide.
		Charted depths and drying heights on nautical charts are given relative to chart datum.
	en.wikipedia.org /wiki/Chart_datum (160 words)

	Geodetic system - Wikipedia, the free encyclopedia
		The main reason that there are a number of datums is that before the advent of GPS positioning, national map making organisations did not have a common surveying reference point and only produced maps for their locality.
		In surveying and geodesy, a datum is a reference point or surface against which position measurements are made, and an associated model of the shape of the earth for computing positions.
		On nautical charts, depths of water are relative to chart datum which is generally the lowest tide caused by gravity alone.
	en.wikipedia.org /wiki/Datum (747 words)

	CHS-Vertical Datums
		The choice of a chart datum is usually more difficult on inland waters than on coastal waters because inland waters lack the stabilizing influence the huge ocean reservoir exerts on the mean water level.
		Chart datum must be set with the low-stage years in mind and may appear pessimistically low during high-stage years.
		Along a river, chart datum is a sloping surface that approximates the slope of the river surface at low stage.
	www.lau.chs-shc.dfo-mpo.gc.ca /english/VerticalDatums.shtml (870 words)

	Introduction
		CHART DATUM is the plane of reference for soundings and is stated in the title of each chart.
		Chart datum is the low water plane to which are referenced the depths of water over features permanently covered by the sea and the elevations of those features which are periodically covered and uncovered.
		The name and date of the horizontal datum used for a chart are shown in the title with a statement, as appropriate, about the corrections to be applied to the geographical positions to convert them to the international reference system of the internationally recognized regional datum.
	www.charts.gc.ca /pub/en/products/Chart1 (988 words)

	The Port of London Authority - Maritime
		Chart Datum is also the level to which tidal levels and predictions are measured and is the same as the zero of the tidal predictions.
		This refers all chart datum levels to a common, national horizontal plane and allows the levels to be checked.
		A chart datum value is dependant upon the range of the tide at a particular location.
	www.portoflondon.co.uk /display_fixedpage.cfm/id/264/site/maritime (503 words)

	Chart Datum - South Africa
		The Tidal Chart Datum is calculated and published by the Hydrographic Office of the South African Navy.
		In fact, the 2002 predictions were calculated as per the new chart datum as well as published in hard copy in the official South African Tide Tables guide.
		Unfortunately however, it was omitted to make mention of the fact that the chart datum had changed with the result that a reader would be under the impression that the Tidal Chart Datum for 2002 would be the same as the datum which had been applicable since 1998.
	www.satides.co.za /chartDatum.html (581 words)

	UKDivers.net - Charts
		His chart was designed for sailors and constructed by wrapping a cylinder around the planet so that it touches the equator.
		Chart Sounding Datum: The tidal datum to which soundings and drying heights on a chart are referred.
		Often shortened to 'chart datum' when it is clear that reference is not being made to a horizontal datum.
	www.ukdivers.net /chartwork/charts.htm (1354 words)

	C-MAP UK - The Electronic Charts Standard - Datum
		The datum used varies from country to country and occassionally the paper chart may not even have a known datum due to the fact that it was last surveyed many, many years ago.
		If the paper chart datum is known, then often there will be a note on the chart that gives the Lat/Lon offset of this datum to WGS84 the most commonly used world wide datum that all GPS units support.
		If you are using a chart plotter that does not have a built-in GPS, it is very important that you know the datum the GPS is working in and that you tell the chart plotter what this datum is by setting the GPS Datum option in one of the setup menus.
	www.c-map.co.uk /forum/topic.asp?TOPIC_ID=15 (437 words)

	The Huntingfield Map Collection
		This is edition 31 of NOAA chart 12222 covering the entrance to Chesapeake Bay from Cape Charles to Norfolk Harbor and north to the entrance to the York River.
		This is edition 57 of NOAA chart 12221 covering the entrance to Chesapeake Bay to north of Mobjack Bay and the Atlantic Ocean from Hog Island to south of Cape Henry.
		This is edition 46 of NOAA chart 12221 covering the entrance to Chesapeake Bay to north of Mobjeck Bay and the Atlantic Ocean from Hog Island to south of Cape Henry.
	www.mdarchives.state.md.us /msa/speccol/1399/carto/html/noaa.html (3121 words)

	TSB Reports - Marine 2000 - M00C0069
		The chart was geographically referenced to an astronomic observation spot on Stony Islet; thus the chart is referenced to an "orphan" or "unknown" horizontal datum.
		Consequently, unless the GPS receiver datum is the same as the chart datum, the receiver datum must be converted to the chart datum for position accuracy.
		While chart datum information is recorded on buoy data cards, the datum selected on the GPS to obtain the position is not always recorded on board Canadian Coast Guard (CCG) vessels nor is there a mandatory field for such an entry.
	www.bst.gc.ca /en/reports/marine/2000/m00n0098/m00n0098.asp?print_view=1 (6960 words)

	Horizontal Chart Datums and Position Accuracy - # 02/2002 - Ship Safety Bulletin - Marine Safety (Site not responding. Last check: 2007-10-11)
		Charts use various horizontal datums as a reference for specifying geographical positions.
		For this reason mariners must ensure the datum in use is consistent with the chart datum.
		Unless the receiver datum is the same as the chart datum, or the position is converted, an inaccurate and misleading position will be plotted.
	www.tc.gc.ca /MarineSafety/bulletins/2002/02_e.htm (443 words)

	The Chart Room
		The chart room is usually a small room adjacent to the pilot house on a vessel where charts and navigation instruments are stored.
		Chart datums can also play a role in plotting GPS positions or transferring positions from one chart to another.
		When transferring positions from one chart to another navigators have always had to determine if a correction to adjust for different chart datums was necessary.
	www.mukilteoyachtclub.com /ChartRoom.htm (645 words)

	Rideau Canal Waterway - Article - Water, Water Everywhere (Site not responding. Last check: 2007-10-11)
		Chart datum is the low water level of the lakes and rivers.
		So, when you are looking at your chart, the depths shown are based on low water level and 95% of the time, the water depths should in fact be deeper than those shown on the chart.
		Datum for a lake is a horizontal surface, datum for a river is a sloping surface, following the slope of the river at low water.
	www.rideau-info.com /canal/articles/water-levels.html (1436 words)

	About GPS
		For instance, when charting a South Seas lagoon, a nineteenth century surveyor could only reference the chart to a datum point somewhere on the shore of the lagoon; he could not accurately position that datum point in relation to the surface of the earth.
		When charts were drawn to the new datum, cartographers discovered that the positions of geographic features on charts drawn to the older datum could not be reconciled with their positions on new charts—the lines of latitude and longitude on the older charts were in the wrong places.
		Notices suddenly appeared on charts indicating the datum to which the chart was drawn, as well as the degree of correction to be applied to older charts to reconcile them with the new navigation systems.
	www.shipwrite.bc.ca /aboutgps.htm (5046 words)

	Chuck Husick on BoatUScom
		The rule is simple; never apply a GPS position to a chart without first ensuring that the GPS datum in use agrees with the datum used to construct the chart.
		Where the datum is not in memory it will be necessary to use a reference text to manually enter the offsets between calculated position and chart position.
		Charts for many areas frequented by small craft are seriously outdated, major shifts in shoals may have occurred since the chart was drawn.
	www.boatus.com /husick/n_gpschart.asp (789 words)

	C-MAP Australia (Site not responding. Last check: 2007-10-11)
		Today there are at least a hundred different datums in use (some date back to surveys conducted by Captain James Cook at the end of the Eighteenth century), and this can cause great inaccuracies when referencing one chart to another while navigating.
		Simply select the datum on the GPS to correspond with the chart on screen, or leave the GPS alone and adjust the datum on the charting system.
		On an electronic chart that doesn't identify datum, an adjustment can still be made between the GPS and the electronic chart, but not until you actually pull up alongside a point like a buoy and reference it to the screen to note where you are.
	www.c-map.com.au /cm_custserv_faq2.asp?divisionID=6&faqProductID=20 (576 words)

	Marine navigation courses: the nautical chart - RYA & ASA sailing schools in Greece
		The angles between three objects in the chart should be the same as the angles between the real objects which they represent.
		The Mercator chart was designed for sailors and can be constructed by wrapping a cylinder around the planet so that it touches the equator.
		Chart sounding datum: The tidal datum (fictitious plane) to which soundings, heights, elevations and drying heights on a chart are referred.
	www.sailingissues.com /navcourse2.html (1886 words)

	SailNet Articles (Site not responding. Last check: 2007-10-11)
		The difference between the datum of the chart and the datum selected in your GPS unit can have a significant impact on navigational accuracy.
		Geographic datum is a frame of reference used by cartographers to define a chart's grid of coordinates.
		In other parts of the world, charts are based on different formats such as WGS 72 or their local and regional datums.
	www.sailnet.com /collections/articles/index.cfm?articleid=sexton012 (636 words)

	Coastal navigation - Mercator chart: 2 nautical charts.
		On a Gnomeric chart this same loxodrome is an arc, while your shortest route (a great circle) ends up as a straight line.
		Horizontal Geodetic Datum: Defines the relationship between the ellipsoid adopted as the model of the Earth's shape, and the Earth itself.
		Corrections: Each chart is liable to corrections which are published by either a national body or the publisher of the nautical chart.
	www.sailingissues.com /courses/navigationcourse2.html (1821 words)

	FAQ: What is a map datum? Which map datum do I use? (Site not responding. Last check: 2007-10-11)
		If you are comparing GPS coordinates to a chart or map, the map datum in the GPS unit must be set to match the chart or map's datum for accurate comparison.
		A datum is a mathematical model of the Earth which approximates the shape of the Earth, and enables calculations such as position and area to be carried out in a consistent and accurate manner.
		The datum is physically represented by a framework of ground monuments (i.e., trig stations) whose positions have been accurately measured and calculated on this reference surface.
	www.garmin.com /support/faqs/faq.jsp?faq=17&webPage=Main+web+page (249 words)

	Spring tides, neap tides and chart datum: 6 tides.
		Spring tides, neap tides and chart datum: 6 tides.
		Depths are usually described with respect to low water reference planes (yielding lower charted depths, which are safer) and heights are shown with respect to high water reference planes (again, yielding lower vertical clearances on the chart, which are safer).
		In this example the Charted Depths are related to LAT.
	www.sailingissues.com /navcourse6.html (1318 words)

	GIS Data, Jobs, Software, News, and Fun - GeoCommunity
		Many charts in the Japan and Korea area referenced to the Tokyo datum, for which positions must be shifted more than 700 meters horizontally to convert to WGS 84 datum.
		Thus, the logical datum shift to WGS 84 can be quite large, depending on the area of the world and the local datum in use, as in the case of the Tokyo datum.
		Some NIMA charts that are not currently based on WGS 84 datum include a note that specifies the necessary adjustment in position to correctly place a WGS 84 position on the chart.
	www.geocomm.com /channel/gps/news/nimagps2 (1733 words)

	Australian Tides Manual (Site not responding. Last check: 2007-10-11)
		Chart recorders are gradually being replaced by some form of shaft encoder coupled with a digital recording device.
		Another problem discussed on Section 2.2 is that of datum control with pressure gauges, particularly in light of the general tendency of the transducers to drift.
		The resulting datum surface, with minor modifications in two metropolitan areas, has been termed the Australian Height Datum (AHD) and was adopted by the National Mapping Council at its twenty-ninth meeting in May 1971 as the datum to which all vertical control for mapping is to be referred.
	www.icsm.gov.au /icsm/tides/SP9/SP920041116.html (7332 words)

	NTSLF \| Chart datum and ordnance datum
		Tidal levels are quoted relative to chart datum (approximately the lowest level due to astronomical effects and excluding meteorological effects).
		The heights of chart datum (CD) relative to ordnance datum (OD, at Newlyn) in the UK are listed below.
		If for example, you have a data value for Liverpool of 1m relative to CD and want to convert it to be relative to OD, then this would be -3.93m (i.e., 1m - 4.93m).
	www.pol.ac.uk /ntslf/tides/datum.html (73 words)

	[No title]
		Chart Datum is not at a fixed level are relative to 23 the land, i.e.
		This is easily done as local Chart Datum 14 is always related to Ordnance Datum, the offset being shown 15 on all charts in a box entitled "Tidal Levels referred to 16 Datums of Soundings", and is also in the Admiralty Tide 17 Tables Volume 1, Supplementary Tables, Table 3.
		All soundings covered by the Western Approaches 17 and the Thorn Channel are related to Chart Datum by reference 18 to the recording gauge at Calshot.
	www.planning-inspectorate.gov.uk /dibden/transcript/pm3rdseptember2002.doc (17996 words)

	Technical Support
		Answer: Probably the chart datum of your GPS is not the same as in WinGPS Pro.
		Scans of Lambert (aviation) charts, ANWB water charts and charts of the Rijnatlas are considered to be suitable.
		DKW charts on the other hand are complete full charts in mostly *.bmp format, best running in 256 colors.
	www.stentec.com /support/wingpspro_dkw/faq_wingpspro_dkw_all_i.html (3589 words)

	Tide, Sun, Moon Glossary
		The surface is called a tidal datum when referred to a certain phase of the tide.
		The mean surface water level determined by averaging heights at all stages of the tide over a 19-year period.
		Mean sea level is usually determined from hourly height readings measured from a fixed predetermined reference level (chart datum).
	www.usm.edu /gcrl/MStide/tideglos.htm (1403 words)

	: Index
		ChartBean is the abstract superclass of all KavaChart charting beans.
		Constructor for label charts that use both X and Y. Dataset(String, double[], int, Globals) - Constructor for class javachart.chart.
		The Datum class is used as the basic KavaChart data storage unit.
	www.dartmouth.edu /~sas/KavaChart/javachart/api/index-all.html (3259 words)

	marksGB (Site not responding. Last check: 2007-10-11)
		The height of any spot located above Chart Datum is called drying height and in underlined on charts.
		The depth of any spot below this level is called charted depth and is not underlined.
		Divers or fishermen interested in deeper areas will soon be interested in the mark option, using a charted depth instead of a drying height.
	p.pellot.free.fr /theomark/marksgb.htm (325 words)

	Chart Datum (Site not responding. Last check: 2007-10-11)
		The numbers printed over the water areas on a chart indicate the minimum amount of water you could expect to find on that spot on the earths surface at any time.
		These depth are measured in fathoms and feet (on an imperial chart) and in meters and decimals of a metre (on a metric chart).
		This is an imaginary line and all water below datum is called a sounding and water above datum is called tide Datum is at 0.0 tide (no tide).
	www.boatlicence.au.com /datum.htm (172 words)

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