Nature of anomalies present in free air gravity and their corresponding anomalies in Bouguer gravity over continents are analysed in light of isostatic compensation of topographic masses. These anomalies are classified into regional, residual and local and criteria are evolved to identify them. The regional anomaly corresponds to regional topography that is compensated. The local anomaly is related to local topographic relief. Residual anomaly is caused by subsurface anomalous source in the form of excess or deficit mass and which is of our interest. A new approach is suggested wherein using zero free air values, regional, residual and local anomalies could be separated. This is illustrated for two gravity profiles where the residuals obtained are compared with isostatic anomalies. Limitations of this method are discussed.