"Accurate" is a loaded question. Survey-grade (expensive) GPS receivers can provide cm accuracy under tree canopies, but others (inexpensive receivers and cell phones) may have 5-10 m accuracy. So, it depends on your comfort level with "accuracy." Please see www.gps-test-site.uga.edu for more papers on GPS accuracy under forest canopies.

You might try aerial LiDAR for landscape mapping of surface and vegetation. Ground based LiDAR if mapping small areas or detailed features. I am not up to date on GPS improvements, but we used to have GPS problems under full canopy about a decade ago, have to wait to capture satellite coverage, etc. On a few occasions, the IPad with Avenza app. did pretty good at locating features during ground surveys with some canopy coverage. There are apparent ways to improve coverage using ground based microwave towers. Land surveyors are typically familiar with the most up-to-date techniques and methods to achieve varying degrees of accuracy and precision. You might find high definition aerial photos also useful or complementary to other methods if the canopy is not uniform -- sometimes individual tree canopies can be located.

Hi Sijeh, I have parts of this route totaly cover by threes, both devices are fine for normal life use. https://gymnica.upol.cz/artkey/gym-201903-0001_the_comparison_of_holux_and_qstarz_gps_receivers_in_free_living_conditions_dynamic_accuracy_in_different_activ.php

Garmin GPS 76 map

Please check for the most recent Garmin GPS, I think even Garmin 76 GPS is not very

recent again.

Garmin GPS 85