What does “spatial resolution” mean? Some answers using MARGINS data Juan Baztan MARINE SCIENCES FOR SOCIETY Place Nicolas Copernic, IUEM Plouzane, France society.org DATA from the University of New Hampshire's Centre for Coastal and Ocean Mapping Marianas Western Insular Margin The maps have been generated by “GeoMapApp,”:

Definitions as introduction: The “spatial resolution” is a measure of the smallest area identifiable on the image. Resolution refers to the sharpness of an image, to the capability of making the individual parts distinguishable. The unit of information is a Pixel. What does “spatial resolution” mean? ? A surface with 9 pixels A surface with 63 pixels A pixel

The pixels are arranged in a grid: What does “resolution” mean? The grid defines geographic space as an array of points arranged in rows and columns. A grid with 8 columns and 10 rows This image is generated from the grid with 80 points, 8 columns and 10 rows. The image has 63 pixels

How do MARGINS scientists built images from the sea floor? What is the resolution of those images? What does “resolution” mean? The oceanographers draw the images of the sea floor by collecting points, then generating grids. Each point of a grid has three values: (X, Y, Z)‏ (column, row, value) (longitude, latitude, water depth)‏ The position is done by the number of the column and the number of the row (X, Y). In a map, the rows indicate the latitude and the columns the longitude. X, columns, longitude Y, r o w s, l a t i t u d e

What does “resolution” mean? How do oceanographers collect the “points” from the sea floor? ' 1' 2' 3'... Satellite Altimetry “Calculates” 1 point every 1 minute latitude, that is every 1,852 km Two main methods: Multibeam echo sounder “Samples” 1 point every meter A GRID OF THE SEA FLOOR One pixel = 1,2 miles One pixel = 1 meter Satellite Altimetry Multibeam echo sounder For more info please see slide 10.

What does “resolution” mean? Therefore, the resolution is related to the quantity of points on a surface, equivalent to the size of the pixels. Points and pixels indicate the quantity of information. Low resolutionMedium resolution It means that we can have representations of different resolutions for the same surface of the sea floor

What does “resolution” mean? BUT: What's this colored image?? This is the sea floor in Marianas Western Insular Margin When we increase the number of points,we increase the quantity of data, we decrease the size of the pixels, we increase the resolution and we can recognize some features like volcanoes and submarine valleys. ??

Some exercises about “resolution” Using this example of the Marianas Western Insular Margin, four questions: X and Y relate to the position, Z relate to the depth. Remember: each point of the grid has three values: X, Y, Z How many points are in the grid? How many pixels in the image? What is the size of a pixel? What is the size of the study area? Can you imagine the seascape? Find 5 volcanoes and 2 submarine valleys

Some exercises about “resolution” This example of the Marianas Western Insular Margin has a grid with 1540 points. The image has 1386 pixels Some volcanoes and submarine valleys are indicated. volcano submarine valley Can you imagine your classroom at the same resolution? Try to draw your classroom in a grid with 1540 points: 35 columns by 44 rows. How can we improve the resolution? At this point you realize that this is not a very good resolution...

An open question In this image we have one point every 100 m. This resolution is obtained only in very few places of the world's oceans. The global grid stems from the satellite "predicted bathymetry" one point every 2 kilometers, the sea floor is not measured but calculated. But! a medium grain of sand measures 1 mm. Increasing the number of points, reducing the size of the pixels, we improve the quality of the image What do we really know about the sea floor? Very little! The main part of the world's oceans' surface remains unknown in its detail. DATA from the University of New Hampshire's Centre for Coastal andOcean Mapping Marianas Western Insular Margin The maps have been generated by “GeoMapApp,”:

Other tasks to perform about resolution: Make groups of 3 or 4 students each. Using or search the whole planet for: (i) the area mapped with the highest resolution, (ii) the the area mapped with the lowest resolution and (iii) a zone with intermediate resolution. Each group has to think of 3 examples taken from daily life in terms of standard of resolution (for example if the resolution is two meters, the object can be a car). * * * In the data base mentioned below, find the study area of the Marianas Western Insular Margin: or in Which surveys have been done in this area? What is the resolution of the study area's available grids? Make a longitudinal profile from the deepest part of the study area to the shallowest. Compare this profile, in terms of resolution, with the one used in Laura Reiser's minilesson: “Profiling Earth's Surface using GeoMapApp“Profiling Earth's Surface using GeoMapApp * How is it possible to improve the resolution of the data from our planet's submarine part?