ArcGIS is the best software to create bathymetry contour and overlay on other raster images or vectors. Bathymetry data available in many websites ). Do you already have bathymetric data as point files or raster? If so, you can easily contour and overlay in just about any GIS program such as ArcGIS, Q, etc @Dan Hirsh Shugar: I do have gridded bathymetric dataset. I need to know how to create contours from gridded dataset and overlay it on MODIS chla dataset and which tool or software is easy to do it? I will check out and see. If you can’t get a copy of ArcGIS, try QGIS. It’s completely free. SAGA GIS is also free but perhaps a little more confusing to learn. Dear Nitish, following link will provide you bathymetry data. View, download and generate contours using QGIS suggested by Hirsh Shugar, if you don’t have ArcGIS. http://ferret.pmel.noaa.gov/NVODS/UI.vm#panelHeaderHidden=false,differences=false,autoContour=false,xCATID=CAFA99223222D59FB6BF29705FAFDDBE,xDSID=dbdb5_top_bathy_nc,varid=bath,imageSize=auto,over=xy,compute=Nonetoken,catid=CAFA99223222D59FB6BF29705FAFDDBE,dsid=dbdb5_top_bathy_nc,varid=bath,avarcount=0,xlo=-0.039999999999992,xhi=359.96,ylo=-90,yhi=90,operation_id=Plot_2D_XY_zoom,view=xy I am using ArcGIS and surfer, you can do one thing, contour plot using with surfer and overlay modis image using with arcgis tool, it is too simple. Source.