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Layer: IE_GSI_MI_Marine_Download_Seabed_Survey_Leg_Data_IE_Waters_WGS84 (ID: 0)

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Name: IE_GSI_MI_Marine_Download_Seabed_Survey_Leg_Data_IE_Waters_WGS84

Display Field: VESSELNAME

Type: Feature Layer

Geometry Type: esriGeometryPolygon

Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P STYLE="margin:8 0 0 0;"><SPAN>This data shows</SPAN><SPAN> areas where</SPAN><SPAN> survey leg report and bathymetry, backscatter and sub-bottom profile data</SPAN><SPAN> </SPAN><SPAN>exists and allows you to download the data. </SPAN><SPAN>The data was collected between </SPAN><SPAN>1996</SPAN><SPAN> and 2021.</SPAN></P><P STYLE="margin:8 0 0 0;"><SPAN><SPAN>Bathymetry is the measurement of how deep is the sea. Bathymetry is the study of the shape and features of the seabed. The name comes from Greek words meaning "deep" and “measure". </SPAN></SPAN></P><P STYLE="margin:8 0 0 0;"><SPAN>Bathymetry is collected on board boats working at sea and airplanes over land and coastline. The boats use special equipment called a multibeam echosounder. A multibeam echosounder is a type of sonar that is used to map the seabed. Sound waves are emitted in a fan shape beneath the boat. The amount of time it takes for the sound waves to bounce off the bottom of the sea and return to a receiver is used to determine water depth. The strength of the sound wave is used to determine how hard the bottom of the sea is. In other words, backscatter is the measure of sound that is reflected by the seafloor and received by the sonar. A strong sound wave indicates a hard surface (rocks, gravel), and a weak return signal indicates a soft surface (silt, mud).</SPAN><SPAN> </SPAN><SPAN /></P><P STYLE="margin:8 0 0 0;"><SPAN>Another piece of equipment is used called a sub-bottom profiler.</SPAN><SPAN>Sub-bottom profile data shows the rock features and the sediment layers that are below the seabed. </SPAN></P><P STYLE="margin:8 0 0 0;"><SPAN /><SPAN /></P><P STYLE="margin:0 0 0 0;"><SPAN>LiDAR is another way to map the seabed, using airplanes. Two laser light beams are emitted from a sensor on-board an airplane. The red beam reaches the water surface and bounces back; while the green beam penetrates the water hits the seabed and bounces back. The difference in time between the two beams returning allows the water depth to be calculated. LiDAR is only suitable for shallow waters (up to 30m depth).</SPAN></P><P STYLE="margin:0 0 0 0;"><SPAN /></P><P STYLE="margin:0 0 0 0;"><SPAN>This data shows areas which have data available for download in Irish waters. </SPAN></P><P STYLE="margin:0 0 0 0;"><SPAN /></P><P STYLE="margin:0 0 0 0;"><SPAN><SPAN>It is a vector dataset. Vector data portray the world using points, lines, and polygons (areas).</SPAN></SPAN></P><P STYLE="margin:0 0 0 0;"><SPAN>This data is shown as polygons. Each polygon holds information on the </SPAN><SPAN>survey leg details (name, vessel, year,date etc). It also provides links where available to download </SPAN><SPAN>bathymetry</SPAN><SPAN> </SPAN><SPAN>(GEOTIFF, ESRI GRID</SPAN><SPAN>, xyz</SPAN><SPAN>),</SPAN><SPAN> </SPAN><SPAN>backscatter</SPAN><SPAN> </SPAN><SPAN>(GEOTIFF), survey report (pdf) and sub-bottom profile (SEGY) data in various formats.</SPAN></P><P STYLE="margin:0 0 0 0;"><SPAN /></P><P STYLE="margin:0 0 0 0;"><SPAN><SPAN>The data available for download are raster datasets. Raster data is another name for gridded data. Raster data stores information in pixels (grid cells). Each raster grid makes up a matrix of cells (or pixels) organised into rows and columns.</SPAN></SPAN></P><P STYLE="margin:0 0 0 0;"><SPAN /><SPAN /></P><P STYLE="margin:0 0 0 0;"><SPAN>This data was collected using a boat or plane. Data is output in xyz format. X and Y are the location and Z is the depth or backscatter value. A software package converts it into gridded data. The grid cell size varies. </SPAN><SPAN>If the </SPAN><SPAN>resolution</SPAN><SPAN> is </SPAN><SPAN>10m </SPAN><SPAN> - </SPAN><SPAN> Each grid cell size is 10 meter by 10 meter. This means that each cell (pixel) represents an area of 10 meter squared.</SPAN></P><P STYLE="margin:0 0 0 0;"><SPAN /></P><P STYLE="margin:0 0 0 0;"><SPAN><SPAN>ESRI GRID datasets contain the depth value. This means you can click on a location and get its depth.</SPAN></SPAN></P><P STYLE="margin:8 0 0 0;"><SPAN>GEOTIFFS are images of the data and only record colour values. We use software to create a 3D effect of what the seabed looks like. By using vertical exaggeration, artificial sun-shading (mostly as if there is a light source in the northwest) and colouring the depths using colour maps, it is possible to highlight the subtle relief of the seabed. The darker shading represents a deeper depths and lighter shading represents shallower depths.</SPAN></P><P STYLE="margin:8 0 0 0;"><SPAN>The gridded XYZ data is also available.</SPAN></P><P STYLE="margin:8 0 0 0;"><SPAN /></P><P STYLE="margin:0 0 0 0;"><SPAN>This data shows areas that have been surveyed. There are plans to fill in the missing areas between 2020 and 2026. The deeper offshore waters were mapped as part of the Irish National Seabed Survey (INSS) between 1999 and 2005. INtegrated Mapping FOr the Sustainable Development of Ireland's MArine Resource (INFOMAR) is mapping the inshore areas. (2006 - 2026).</SPAN></P></DIV></DIV></DIV>

Service Item Id: 5708fce5742942f09478ac6f6a3767df

Copyright Text: Contains Irish Public Sector Data (Geological Survey Ireland & Marine Institute) licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) licence

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