Use this forum

https://www.cfd-online.com/

Whenever there is a coastline you have no chance whatsoever in finding a precise measure - since the result depends crucially upon how you measure the coastline: see 

https://en.wikipedia.org/wiki/Coastline_paradox

I think you can extract an image, then you can change it from raster to vector. by editing the vector and cartography, you can create the boundaries by ArcGIS software. You can also use the 'Raster Domain' tool. This will produce a polygon or polyline boundary shapefile/feature class from a raster file. You can also create a mosaic dataset in a geodatabase but this method is not easy. You can also use the software of spatialecology.com, to generate a polyline for the raster edge.You can also draw them based on that image. Also, check the link. Regards.

https://www.google.com/maps/d/viewer?mid=1zLt4ISerYUAzL3qS5-vNA0i34zA&hl=en&ll=-37.792534239941425%2C144.9870229999999&z=13

Well Ali,

It does not make any difference which software you use - there is NO "correct" measure of any shoreline's length. It's a question you just have to give up ever getting an answer to: because there is NONE.

I was trying to extract boundaries from googlemaps (not necessarily coastlines but administrative boundaries or even watersheds), but it seems that googlemaps does not allow it. I wanted to use such extracted boundaries to ArcGIS to make my work convenient. So what else could I do anyway regarding extracting boundaries? Thanks for your kind effort to answer my queries. 

Dear Michael Patriksson,

I know the fractal-like properties of coastlines and tiny fractions, there is no well-defined length and it depends on the scale of measurement. In practice, you can extract the edges of the spatial features. The exact mathematical length is not required in several engineering cases. You also can generalize and smooth the boundaries of spatial entities. Also, you can have an "estimation" of the length. Consider this fact that however, you should be able to generate the map of the cities. In cartography, they can generate the map of the world. You can check the following link to see the definitions and porpuses of cartography. In cartography, they say: "you should eliminate characteristics of the mapped object that are not relevant to the map's purpose". you can also check "cartographic generalization or map generalization. " generalization seeks to abstract spatial information at a high level of detail to information that can be rendered on a map at a lower level of detail." You can check the second link.

https://en.wikipedia.org/wiki/Cartography

https://en.wikipedia.org/wiki/Cartographic_generalization