How accurate are measurements in Google Earth?
Apparently, the measurment ruler is not accurate over long distances > 5,000 km.
Google's offical stance says, "makes no claims as to the accuracy of the coordinates in Google Earth. These are provided for entertainment only and should not be used for any navigational or other purpose requiring any accuracy whatsoever".
I know this topic is kinda old, but I think my comment can help other fellas that have this doubt.
In 2011 two brazilians published an article about it, and they concluded that:
*the error is just 0,44% for line measurements; *the error is just 3,54% for polygon measurements; *the error is just 1,39% for perimeters calculation;
Based on these results they concluded that you can use Google Earth as a good source for mapping in scales smaller than 1:150000, assuming the planimetrical error as 0,1 mm.
Of course this is just a case of study, and these results depend on your area of study. I suppose that in the US the results may be even better.
Source: Lopes, E. E.; Nogueira, R. E. Proposta Metodológica para validação de imagens de alta resolução do Google Earth para produção de mapas. In: Simpósio Brasileiro de Sensoriamento Remoto, 10, Curitiba, PR, 2011. Anais: São José dos Campos: INPE, 2011.
Source link (in portuguese): https://www.researchgate.net/profile/Ruth_Nogueira/publication/266032536_Proposta_Metodologica_para_Validacao_de_Imagens_de_Alta_Resolucao_do_Google_Earth_para_a_Producao_de_Mapas/links/54ff4e900cf2672e224563eb/Proposta-Metodologica-para-Validacao-de-Imagens-de-Alta-Resolucao-do-Google-Earth-para-a-Producao-de-Mapas.pdf
After just installing a break water and knowing all the dimensions, i checked it on google earth to see how close the eye in the sky is, on 470 ft it showed 477 ft, I tried google earth pro it did not make a difference. I have used it before and it seemed the accuracy was better. The location used was 48d38'59.33"N x 123d33'07.23"W The long leg of the east to west break water sections is accually 470'7" x 20' wide.